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NORTH  CAROLINA  STATE  UNIVERSITY  LIBRARIES 


S02514748  V 


Date  Due 


VOL.  I. 


PI.  ! 


% 


7 


OENOTHERA     LAMARCKIANA, 
A  Mutating  Species. 


M^tinHood&LarkiniittLondon.WC. 


VOL.  I. 


PL  II. 


OENOTHERA     GIGAS 
Originated  in  1895. 


M:artin.Hood&Larkiniitli.London,WC. 


VOL.  I. 


PL  III. 


OENOTHERA     ALBIDA, 
Produced  Yearly  by  the  Parent-Species. 


Martin, Ho  ad  &LarkinJ.ith,Loiidon.W.C. 


VOL.  I. 


PL  IV. 


A    MUTATION     IN    A    FAMILY    OF    OENOTHERA    LATA. 

Origin  of  Oenothera  albida. 


Martin.Hood&Larldn^Litt.London.W.C. 


VOL.  I. 


PL  V. 


I 


OENOTHERA     SCI  NTI  LEANS. 


od  &LarkinLitli,London.W.C . 


VOL.  I. 


PI.  VI. 


'  i 


J^^. 


OENOTHERA     OBLONGA. 


Ptin.Hocii&l,arkiniith,LoiidDn,W.C. 


THE 


MUTATION  THEORY 


EXPERIMENTS  AND  OBSERVATIONS 

ON  THE 

ORIGIN  OF  SPECIES  IN  THE  VEGETABLE 

KINGDOM 


BY 

HUGO  DE  VRIES 

PROFESSOR    OF    BOTANY    AT    AMSTERDAM 


TRANSLATED  BY 

PROF.  J.  B.  FARMER  AND  A.  D.  DARBISHIRE 


VOLUME  I 


THE  ORIGIN  OF  SPECIES  BY  MUTATION 

WITH  NUMEROUS  ILLUSTRATIONS  AND  FOUR  COLORED  PLATES 


CHICAGO 

THE  OPEN  COURT  PUBLISHING  COMPANY 

LONDON    AGENTS 
KEGAN  PAUL^  TRENCH,  TRUBNER  &  CO.,  LTD. 

1909 


COPYRIGHT  BY 

The  Open  Court  Publishing  Co. 
1909 


AUTHOR'S  PREFACE  TO  THE  TRANSLATION. 

The  promulgation  of  the  principle  of  unit-characters  is 
the  main  theme  of  this  work,  as  is  emphasized  in  the  first 
sentence  of  the  Introduction.  At  the  time  of  the  publication 
of  the  first  part  of  the  German  edition  (1900)  this  principle 
was  new  and  was  also  in  evident  opposition  to  the  current 
belief  in  the  slow  and  gradual  evolution  of  the  organic  world. 
During  the  years  that  have  since  elapsed,  it  has  gained  almost 
universal  acceptance,  though  there  are  still  some  authors, 
especially  among  zoologists,  who  are  opposed  to  it. 

The  evidence  which  supported  this  view  was  derived 
from  three  main  sources. 

First  a  clearer  understanding  of  the  processes  of  selec- 
tion in  agricultural  plant-breeding.  This  conception  has 
since  been  corroborated  in  the  most  convincing  manner  by 
the  work  of  Nilsson  and  of  Korschinsky^  and  it  points  to 
the  elementary  species  as  the  real  material  for  artificial  and 
natural  selection. 

Secondly,  the  experimental  evidence  afforded  by  the 
evening  primroses  and  some  other  groups  of  plants ;  espe- 
cially the  observed  origin  of  Oenothera  gigcts,  which  ap- 
peared suddenly  in  my  cultures  in  the  year  1895  and  pos- 
sessed, at  its  first  origin,  all  the  attributes  of  a  new  species, 
including  constancy  and  even  a  double  number  of  chromo- 
somes in  its  nuclei. 

Thirdly,  the  new  light,  thrown  by  the  principle  of  the 
unit-characters  on  the  work  of  Mendel,  neglected  up   to 


\'-ji 


y 


iv  Author  s  Preface  to  the  Translation. 

that  time,  which  even  Focke  in  his  standard  work  on 
Plant-hybrids  did  not  give  the  rank  of  a  work  of  first-rate 
importance.  The  work  of  Bateson  and  of  his  school,  of 
CuENOT,  Webber  and  many  others,  but  above  all  that  of 
Davenport,  have  since  brought  the  principle  of  unit-char- 
acters to  its  now  prominent  rank  in  the  study  of  hybridi- 
zation. 

There  can  be  no  doubt,  that  this  principle  of  the  unit- 
characters  opens  up  a  wide  range  of  questions  and  subsidiary 
theories,  which  may  now  be  subjected  to  experimental  in- 
quiry and  critical  study.  The  phenomena  of  inheritance 
and  hybridization  constitute  a  wide  field,  which  had  scarcely 
been  explored  hitherto.  Half-  and  middle-races,  with  their 
apparently  incomplete  heredity,  constant  hybrids,  correlated 
and  associated  characters,  and  many  other  most  curious  phe- 
nomena afiford  plenty  of  scope  for  future  investigation. 

Under  these  circumstances  I  feel  deeply  indebted  to  Pro- 
fessor Farmer  and  Mr.  Darbishire  for  their  painstaking 
work  in  preparing  an  English  translation  of  this  book,  as 
well  as  to  Dr.  Paul  Carus  of  the  Open  Court  Publishing 
Co.  for  his  liberality  and  full  confidence  in  the  scientific  and 
practical  value  of  the  principles  enunciated  therein.  Great 
support  has  already  been  accorded  to  my  ideas  by  many 
English  and  American  workers  in  this  field,  and  it  is  con- 
fidently hoped,  that  this  translation  will  secure  that  uni- 
versal cooperation  without  which  no  great  scientific  principle 
can  attain  its  full  measure  of  usefulness  to  mankind. 

No  essential  changes  have  been  made  in  the  translation, 
with  the  exception  of  those  which  have  been  made  necessary 
by  the  work  of  Hj.  Nilsson  on  the  selection  and  the  im- 
provement of  cereals  in  Sweden.  Corrections  of  minor 
points  have  been  introduced  wherever  necessary. 

It  is  proposed  to  publish  this  translation  in  two  inde- 
pendent volumes,  the  first  dealing  Avith  the  origin  of  spe- 
cies by  mutation,  the  second  with  the  origin  of  varieties 
and  with  the  general  considerations  found  at  the  end  of  the 


Author's  Preface  to  the  Translation.  v 

German  edition.  Some  chapters,  especially  among  those  on 
hybridization,  which  seem  to  be  of  too  technical  a  nature  for 
the  general  student,  will  be  omitted  from  the  second  volume. 
It  is  proposed  to  publish  their  translation  in  a  separate  work. 
Amsterdam^  June  1908. 

Hugo  de  Vries. 


TRANSLATORS'  PREFACE. 

The  task  of  preparing'  this  translation  has  been  made 
Hghter  by  the  knowledge  that  the  need  for  it  is  urgent. 
Professor  De  Vries's  successful  attempt  to  bring  the  pro- 
cess of  specific  differentiation  within  the  sphere  of  experi- 
mental inquiry  is  now  recognized  as  a  landmark  in  the 
history  of  our  knowledge  of  these  phenomena.  But  those 
who  take  part  in  the  discussion  of  evolutionary  questions 
are  rarely  equipped  with  even  a  superficial  familiarity  with 
the  broad  features  of  Professor  De  Vries^s  investigations 
and  ideas,  and,  still  less,  with  (what  should  be  a  minimum 
qualification  for  a  participant  in  such  discussions)  a  de- 
tailed knowledge  of  the  contents  of  Die  Mutationstheorie. 

It  is  hoped  that  this  translation  will  help  to  remedy  this 
state  of  affairs.  This  much,  at  any  rate,  is  certain,  that  the 
evidence,  collected  by  De  Vries  up  to  1901,  bearing  on  the 
question  of  the  origin  of  species  and  varieties  by  mutation, 
is  now  for  the  first  time  available  to  the  student  of  evolution 
who  cannot  read  German. 

In  the  translation  itself  we  have  endeavored  to  convey 
the  author's  meaning  as  faithfully  as  possible  rather  than 
to  provide  a  word  for  word  translation  of  the  German. 
And  to  this  end  we  have,  wherever  it  seemed  necessary, 
split  sentences  into  two,  or  run  two  into  one,  or  made  other 
such  additions  and  omissions  as  seemed  desirable.  All  of 
these  alterations  have  been  examined  and  approved  by  the 
author. 


Translators'  Preface.  vii 

We  hope  that  our  translation  of  this  great  work  will 
help  to  bring  us  closer  to  an  understanding  of  one  of  the 
most  puzzling  manifestations  of  vital  activity — that  of  spe- 
cific diversity. 

J.  B.  Farater. 

A.   D.   Darbishire. 


PREFACE  TO  THE  FIRST  VOLUME. 

The  origin  of  species  has  so  far  been  the  object  of  com- 
parative study  only.  It  is  generally  believed  that  this  highly 
important  phenomenon  does  not  lend  itself  to  direct  obser- 
vation, and,  much  less,  to  experimental  investigation. 

This  belief  has  its  root  in  the  prevalent  form  of  the  con- 
ception of  species  and  in  the  opinion  that  the  species  of 
animals  and  plants  have  originated  by  imperceptible  grada- 
tions. These  changes  are  indeed  believed  to  be  so  slow  that 
the  life  of  a  man  is  not  long  enough  to  enable  him  to  witness 
the  origin  of  a  new  form. 

The  object  of  the  present  book  is  to  show  that  species 
arise  by  saltations  and  that  the  individual  saltations  are 
occurrences  which  can  be  observed  like  any  other  physio- 
logical process.  Forms  which  arise  by  a  single  saltation 
are  distinguishable  from  one  another  as  sharply  and  in  as 
many  ways  as  most  of  the  so-called  small  species  and  as 
many  of  the  closely  related  species  of  the  best  systematists, 
including  Linnaeus  himself. 

In  this  way  we  may  hope  to  realize  the  possibility  of 
elucidating,  by  experiment,  the  laws  to  which  the  origin 
of  new  species  conform.  The  results  of  these  studies  can 
then  be  compared  with  those  which  have  been  obtained 
with  systematic,  biological  and  particularly  with  palseonto- 
logical  data.  A  most  remarkable  agreement  will  be  found 
to  exist  between  these  and  my  new  results. 

These   saltations,  or  mutations,   of  which  the   so-called 


Preface  to  the  First  Volume.  ix 

sports  are  the  best  known  instances,  constitute  a  distinct 
province  in  the  study  of  variabiHty.  They  occur  without 
transitional  gradations  and  are  rare ;  whilst  ordinary  varia- 
tions are  continuous  and  always  present. 

The  whole  subject  of  variability,  therefore,  falls  into 
two  sections,  one  of  which  includes  the  ever  present,  indi- 
vidual or  fluctuating  variability,  whilst  the  other  embraces 
mutability.  The  former  phenomena  conform  to  the  well- 
known  laws  of  probability  and  are  determined  by  general 
nutritional  conditions ;  they  also  afford  the  material  for  the 
production  of  many  of  the  so-called  improved  races  of  agri- 
culture. 

Mutations  give  rise  not  only  to  species  but  also  to  varie- 
ties ;  and,  as  has  been  recognized  for  a  long  time,  they  play 
an  all-important  role  in  horticulture.  An  exhaustive  com- 
parative and  experimental  study  of  horticultural  varieties 
is  an  indispensable  preliminary  to  a  complete  treatment  of 
the  problem  of  the  origin  of  new  forms.  It  will  be  given  in 
the  second  volume. 

The  generalizations  here  outlined  apply  obviously  to 
animals  as  well  as  to  plants.  Though  as  a  botanist  I  have 
confined  my  attention  to  the  latter,  I  am  convinced  that 
my  results  will  be  confirmed  in  the  realm  of  the  animal 
kingdom.  Again  a  proper  distinction  between  variability 
and  mutability  is  of  the  greatest  importance  from  the  point 
of  view  of  the  application  of  the  results  of  biological  investi- 
gation to  the  solution  of  sociological  problems.  For,  the 
question  of  the  origin  of  species  has  really  very  little  to  do 
with  these  highly  important  problems ;  whilst  that  of  fiuc- 
tuating  variability  is  intimately  and  fundamentally  bound 
up  with  it. 

The  contrast  between  these  two  groups  of  phenomena, 
variability  (in  the  strict  sense)  and  mutability,  becomes  ob- 
vious when  we  imagine  that  the  properties  of  organisms 
are  built  up  of  perfectly  distinct  and  independent  units. 
The  origin  of  a  new  unit  is  a  mutation ;  but  the  new  unit 


X  Preface  to  the  First  Volume. 

varies  in  the  degree  of  its  manifestation  according  to  the 
same  laws  as  those  to  which  the  elements  of  the  species, 
already  existing,  conform. 

The  properties  of  these  units  can  be  studied  far  more 
conveniently  by  means  of  experiments  in  hybridization  than 
by  merely  observing  or  rather  waiting  for  their  origin.  On 
the  basis  of  this  principle  the  most  complicated  phenomena 
of  hybridization  must  be  explained  by  means  of  the  results 
of  the  simplest  crosses.  For,  by  a  combination  of  these 
simpler  processes  we  may  expect  to  arrive  at  an  elucidation 
of  the  laws  to  which  the  phenomena  of  hybridization  con- 
form, and  ultimately  be  in  a  position  to  predict  the  result 
in  special  cases.  In  this  way  the  application  of  the  theory 
of  mutation  to  the  elucidation  of  the  phenomena  of  hybridi- 
zation will  enable  us  to  ascertain  what  conclusions  relating 
to  the  origin  of  species  the  study  of  these  processes  may 
warrant. 

A  knowledge  of  the  laws  of  mutation  must  sooner  or 
later  lead  to  the  possibility  of  inducing  mutations  at  will 
and  so  of  originating  perfectly  new  characters  in  animals 
and  plants.  And  just  as  the  process  of  selection  has  en- 
abled us  to  produce  improved  races,  greater  in  value  and  in 
beauty,  so  a  control  of  the  mutative  process  will,  it  is  hoped, 
place  in  our  hands  the  power  of  originating  permanently 
improved  species  of  animals  and  plants. 

Hugo  de  Vries. 
Amsterdam^  August  1901. 


CONTENTS. 


PAGE 


Introduction 3 


Erratum. 

Figure  38,  page  191  should  read  figure  37. 


1.  The  Transmutation  Theory  Before  Uakwix lu 

2.  Darwin's  Selection  Theory 28 

3.  Wallace's  Selection  Theory 39 

4.  The  Various  Forms  of  Variability 43 

Polymorphism,  45 ;   Individual  or  Fluctuating  Varia- 
bility, 47 ;  Spontaneous  Variations,  53. 

5.  The  Elements  of  the  Species 56 

The  Variation  of  the  Elementary  Specific  Characters, 
60. 

6.  The  Mutation  Hypothesis 62 

Historical  Review,  62,  Bateson,  63 ;  Scott^  66 ;  Kor- 

SCHINSKY^  68. 

III.    Selection  Alone  Does  Not  Lead  to  the  Origin  of  New 

Species .'. 71 

7.  Selection  in  Agriculture  and  Horticulture 71 

Maize,  71;  Results  of  Chance  Crossings,  yj  \  Novel- 
ties, 78. 

8.  Selective  Breeding  Followed   by  Vegetative  Propagation    82 

Regression,  83. 

9.  On  the  Duration  of  the  Process  of  Selection 85 

10.  Acclimatization 92 

American    Maize    in    Baden,    95;    Degeneration    of 
Races,  97. 

11.  Sugar   Beets 99 


X  Preface  to  the  First  Voliune. 

varies  in  the  degree  of  its  manifestation  according  to  the 
same  laws  as  those  to  which  the  elements  of  the  species, 
already  existing,  conform. 

The  properties  of  these  units  can  be  studied  far  more 
conveniently  by  means  of  experiments  in  hybridization  than 
by  merely  observing  or  rather  waiting  for  their  origin.  On 
the  basis  of  this  principle  the  most  complicated  phenomena 
of  hybridization  must  be  exj^lained  by  means  of  the  results 
of  the  simplest  crosses.     For,  by  a  combination  of  these 


^_j,.xx  v^i  cpv^x^ics  luc  sLuuy  oi  tnese  processes  may 

warrant. 

A  knowledge  of  the  laws  of  mutation  must  sooner  or 
later  lead  to  the  possibility  of  inducing  mutations  at  will 
and  so  of  originating  perfectly  new  characters  in  animals 
and  plants.  And  just  as  the  process  of  selection  has  en- 
abled us  to  produce  improved  races,  greater  in  value  and  in 
beauty,  so  a  control  of  the  mutative  process  will,  it  is  hoped, 
place  in  our  hands  the  power  of  originating  permanently 
improved  species  of  animals  and  plants. 

Hugo  de  Vries. 
Amsterdam,  August  1901. 


CONTENTS. 


PAGE 


Introduction 3 

PART  I. 

THE  PRINCIPLES  OF  THE  CURRENT  THEORY  OF  SELECTION. 

A  REVIEW  OF  THE  FACTS. 

I.    Selection  and  AIutation n 

II.    Mutability  and  Individual  Variation 16 

1.  The  Transmutation  Theory  Before  Darwin 16 

2.  Darwin's  Selection  Theory 28 

3.  Wallace's  Selection  Theory 39 

4.  The  Various  Forms  of  Variability 43 

Polymorphism,  45 ;  Individual  or  Fluctuating  Varia- 
bility, 47 ;  Spontaneous  Variations,  53. 

5.  The  Elements  of  the  Species 56 

The  Variation  of  the  Elementary  Specific  Characters, 
60. 

6.  The  Mutation  Hypothesis 62 

Historical  Review,  62,  Bateson,  63 ;  Scott,  66 ;  Kor- 

SCHINSKY,,  68. 

III.    Selection  Alone  Does  Not  Lead  to  the  Origin  of  New 

Species .'.  , 71 

7.  Selection  in  Agriculture  and  Horticulture 71 

Maize,  71;  Results  of  Chance  Crossings,  77;  Novel- 
ties, 78. 

8.  Selective  Breeding  Followed   by  Vegetative  Propagation     82 

Regression,  83. 

9.  On  the  Duration  of  the  Process  of  Selection 85 

10.  Acclimatization 92 

American    Maize    in    Baden,    95;    Degeneration    of 
Races,  97. 

11.  Sugar   Beets 99 


xii  Contents. 

PAGE 

12.  Cereals io6 

Pedigree  and  Elite,  no;  Nilsson's  Results,  114. 

13.  The  Limits  to  the  Amount  of  Change  that  Can  be  Ef- 

fected by  Selection 118 

Linear  Variation,    118;    Regression,    120;    Instability 
of  Improved  Races,  120;  Adaptation,  121. 

14.  The  Behavior  of  Improved  Races  After  the  Cessation 

of  Selection 122 

Progeny  of  the  Original  Seed,  126;  Change  of  Seed, 
126;  Intermediate  Generations,  128. 

IV.    Controversial  Questions 130 

15.  Acquired  Characters  and  Variations  Caused  by  Nutri- 

tion     130 

16.  On  the  Inheritance  of  Acquired  Characters 135 

Papavcr   somnifcrum   polycephalum,    138;     Selection 
and  Nutrition,  142. 

17.  On    Partial    Variability    and    Selection    by    Vegetative 

Methods  of  Propagation 143 

Alpine  Plants,  145;  Sugar  Cane,  148. 

18.  Variation  and  Adaptation 149 

19.  Variability  in  Man  and  Social  Questions 154 

20.  Some  Subjects  for  Future  Investigation 159 

Correlative  Variation,  160;  External  Conditions,  161; 
Regression,  161 ;  Retrogressive  Selection,  163. 

V.    The  Origin  of  Species  by  Mutation 165 

21.  Species,  Subspecies  and  Varieties 165 

Varieties,   169;  Elementary  Species,   171. 

22.  Species  in  Nature 172 

22).  Species  in  Cultivation 176 

Age  of  Races,  176;   Cereals,   178;   Apples,   179;   Age 
of  Garden  Varieties,  183. 

24.  Species  and  Specific  Characters 185 

25.  Mutations  in  Cultivation 187 

Historical  Accounts  of  the  Origin  of  Species,    188; 
Sterile  Forms,  195 ;  Constancy  from  Seed,  196. 

26.  The  Hypothesis  of  Indiscriminate  Mutability 198 

27.  The  Hypothesis  of  Periodic  Mutability 205 

The  Migration  Theory,  206. 

28.  The  Phenomenon  of  Mutation  Within  the  Limits  of 

the  Mutation  Periods 207 

Delboeuf's  Law,  208. 
VI.    Conclusion 211 


Contents.  xiii 

PART  II. 

THE  ORIGIN    OF   ELEMENTARY   SPECIES    IN   THE   GENUS 

OENOTHERA. 


PAGE 


The   Pedigree  Families 217 

1.  Oenothera  Lamar ckiana,  a  Mutating  Plant  (Plate  I) .  .  217 

2.  The  Lamarckiana-Family 221 

Pedigree,  224. 

3.  The  Mutations  in  the  Lamarckiana-Family 226 

O.  gigas,  226;  O.  Albida,  229;  O.  ruhrinervis,  230; 
O.  oblonga,  234;  O.  nanella,  235  ;  O.  lata,  239;  O.  scin- 
tillans,  243. 

4.  The  Laws  of  Mutation 247 

Sudden  Appearance,  248;  Constancy,  249;  Elemen- 
tary Species,  251;  Indefinite  Direction  of  the  Muta- 
tions, 255. 

5.  A  Branch  of  the  Lamarckiana-Family 259 

Pedigree,  262. 

6.  The  Laevifolia-Family 265 

Original  Locality,  266;  Pedigree,  273. 

7.  Two  Lata-Families   ( Plate  IV) 27S 

O.  ruhrinervis  and  O.  oblonga  from  O.  lata,  283 ; 
Pedigrees,  285,  288. 

8.  Mutations  in  Other  Families 289 

Characters  of  the  Leaves,  293-295 ;  ]\Iutants  from 
Crosses,  298-299. 

9.  Mutations   in   Nature 300 

Beginning  of  the  Mutation  Period,  306. 

II.    The  Origin  of  Each  New  Species  Cosidered  Separately.  308 

A.  The  Two  Older  Species 308 

10.  Oenothera  laevifolia 308 

Crumples  on  the  Leaves,  310. 

11.  Oenothera  brevistylis 315 

B.  The  Constant  New  Species 318 

12.  Oenothera  gigas  (Plate  II) 318 

13.  Oenothera   rubrinervis 3^7 

Units  of  the  Characters,  328. 

14.  Oenothera  oblonga  (Plate  VI) 337 

Mutation  Coefficients,  337. 

15.  Oenothera  albida  (Plates  III  and  IV) 349 

16.  Oenothera    leptocarpa 353 


xiv  Contents. 

PAGE 

17.  Oenothera    semilata 358 

18.  Oenothera  nanella  (O.  Laniarckiana  nanella) 360 

Conception  of  Variety,  360;  Dwarf  Forms,  361; 
Atavism,  2>^2)  \  Constancy,  372 ;  Compound  Types,  375. 

C.  The   Inconstant   Species 277 

19.  Oenothera  scintillans   (Plate  V) ^^yy 

Unfit  Types,  381. 

20.  Oenothera   elUptica 393 

21.  Oenothera    sublinearis 399 

D.  The   Sterile   Species 402 

22.  Oenothera    lata 402 

Units  of  the  Characters,  402. 

2S.  Incipient    Species 416 

Sterility,  417;  O.  spatliulata,  419;  O.  fatua,  420;  O. 
sitbovata,  420. 

III.  The  Systematic  Value  of  the  New  Species 425 

24.  The  Nature  of  the  Boundaries  Between  Related  Spe- 

cies   425 

Transgressive  Variability,  426. 

25.  Transgressive  Variability 430 

Of  the  Petals,  433;  Of  the  Fruits,  436. 

26.  Oenothera  Laniarckiana  seringe 437 

Seeds,  437;  Species  of  Ouagra,  438;  Mutation  Period 
of  O.  biennis,  440;  Diagnosis,  441 ;  O.  grandi flora,  441. 

27.  Synopsis  of  the  Characters  of  the  New  Species 444 

Fruits,  446-447;  Analytical  Tables,  448-454. 

28.  Comparison  of  the   Characters   of  the  Old  and  New 

Species 454 

IV.  On  the  Latent  Capacity  for  Mutation 462 

29.  Repeated  Mutations  Are  the  Result  of  the  Same  Inner 

Causes 462 

30.  The  Latent  Inheritance  of  Other  Characters  in  O.  La-  ■ 

marckiana 468 

Pitchers,  470;  Tricotyly,  474;  Fasciation,  476;  Varie- 
gation of  Leaves,  480;  Polymery,  481;  Other  Devia- 
tions, 484. 

31.  The  Hypothesis  of  a  Premutation  Period 490 

Oenothera  biennis,  495. 

V.    Conclusion 497 

Ways  to  Look  for  Mutable  Plants,  497;  Cultures, 
502;  Intermediate  Forms,  504;  Species  or  Varieties, 
506;  Other  Periods  of  Mutation,  510. 


Contents.  XV 

PART  III. 

NUTRITION  AND  SELECTION. 

'  PAGE 

I.    Simultaneous    Influence   of   Nutrition   and   Selection 

ON  Various  Characters 515 

1.  Variability  as  a  Nutritional  Phenomenon 515 

Sensitive  Period,  521 ;  Nutrition  of  the  Mother- Plant, 
522 ;  Selection  and  Nutrition,  523. 

2.  Methods  of  Investigation 523 

11,    The  Length  of  the  Fruit  of  Oenothera  Lamarckiana.  . .  528 

3.  Correlation  Between  Individual   Strength  and  Length 

of  Fruit 528 

4.  The  Simultaneous  Operation  of  Nutrition  and  Selec- 

tion     536 

Long-fruited  Race,  544;  Short-fruited  Race,  546. 

5.  Shifting  of  the  Curves  of  Variability  by  Nutrition...,  551 

III,    Curves  of  Ray  Florets  of  the  Compositae  and  of  the 

Rays  of  Umbels  in  the  Umbelliferae 556 

6.  Obliteration  of  the  Effect  of  Selection  by  Nutrition. . .   556 

Anethum,  559. 

7.  Equilibrium  Between  the  Effects  of  Selection  and  Nu- 

trition    562 

Chrysanthemum,  563;  Coreopsis,  566;  Bidcns,  567. 

8.  Obliteration  of  the  Effects  of  Nutrition  by  Selection. . .  569 

Coriandnim,  569;  Madia,  571. 

9.  Summary 573 

Index 577 


LITERATURE. 

EARLIER  STUDIES  AND   PRELIMINARY   NOTES  OF   THE   AUTHOR. 

a.  Intracellulare  Pangenesis.    Jena,  1899. 

b.  Fluctuating  Variability. 

Ueber  halbe   Galtoncurven.     Ber.  d.  d.  bot.  Ges.,    1894,    Bd.  XII,   Heft  7. — 

Bot.  Jaarboek,  1895,  \TI,  p.  74. — Archiv.  Need.,  1895,  T.  XXVIII,  p.  442. 
Eenheid  in   Veranderlykheid.   Album  der   Natuur,    1898. — Revue   de  I'uni- 

versite   de   Bruxelles,    1898,   T.   Ill,   p.    5. — University   Chronicle,    1898, 

I,  p.  311. 
Alimentation  et   Selection.    Vol.  Jubil.   Societe  biol.   Paris,    1899,   p.    17. — 

Biol.  Centralblatt,   1900,  XX,  No.  6.   , 
Othonna  crassifolia  (L'Othon)   Botan.  Jaarboek,  1900,  XII,  p.  20. 

c.  Mutability. 

Over  steriele  Maisplanten.     Bot.  Jaarboek,    1889,  I,  p.   141. 

Steriele  Mais  als  erfelyk  ras.      Bot.  Jaarboek,    1890,   II.  p.    109. 

Sur  I'introduction  de  I'Oenothera  Lamarckiana  dans  les  Pays-Bas.      Ned. 

Kruidk.  Archief,   1895,   VI,  p.  4. 
Sur   I'origine  experimentale   d'une  nouvelle  espece  vegetale.      Cps.   rs.   de 

I'Acad.  de  Paris,   1900. 
Sur  la  mutabilite  de  I'Oenothera   Lamarckiana.      Cps.    rs.   de  I'Acad.    de 

Paris,   1900. 
Recherches  experimentales  sur  I'origine  des  especes.      Revue   generale   de 

Botanique,   1901,  T.  XIII,  p.   i. 
Die  Mutationen  und  die  Mutationsperioden  bei  der  Entstehung  der  Arten. 

Vortrag  in  der  Naturf.-Vers.,  Hamburg,   1901.    Leipsic,  Veit  &  Co. 

d.  After  1901. 

Species  and  Varieties;  Their  Origin  by  Mutation,    ist  ed.,    1905;   2d  ed., 

1906;  Chicago,  The  Open  Court  Publishing  Co. 
Plant-Breeding.    Comments  on  the  Experiments  of  Nilsson  and  Burbank, 

1907.     Chicago,  Xhe  Open  Court  Publishing  Co. 
Ueber  die  Dauer  der  Mutationsperiode  bei  Oenothera  Lamarckiana.    Ber. 

d.  d.  bot.  Gesellsch.,   1905,  XXIII,  Heft  8. 
Die     Svalofer     Methode     zur     ^'eredlung     landwirthschaftlicher     Kultur- 

gewachse   und    ihre    Bedeutung   fiir   die    Selektionstheorie.      Archiv    fiir 

Rassen-  und  Gesellschaftsbiologie.     3.  Jahrg.,  Heft  3,    1906. 
Elementary    Species  in  Agriculture.     Proceedings  American   Philosophical 

Society,  Vol.  XLV,   1906,  April   18. 
Aeltere  und  neuere  Selektionsmethode.     Biolog.  Centralblatt,   Bd.  XXVI, 

Nos.  13-15,  1906. 
Die  Neuziichtungen  LuTHER  Burbanks.     Biolog.   Centralbl.,   Bd.   XXVI, 

No.  19,  Sept.  1906. 


INTRODUCTION. 


INTRODUCTION. 

By  the  Mutation  theory  I  mean  the  proposition  that 
the  attributes  of  organisms  consist  of  distinct,  separate 
and  independent  units.  These  units  can  be  associated 
in  groups  and  we  find,  in  alhed  species,  the  same  units 
and  groups  of  units.  Transitions,  such  as  we  so  fre- 
quently meet  with  in  the  external  form  both  of  animals 
and  plants,  are  as  completely  al)sent  between  these  units 
as  they  are  between  the  molecules  of  the  chemist. 

It  is  perhaps  unnecessary  to  remark  that  these  gener- 
alizations refer  to  the  animal  as  well  as  to  the  vegetable 
kingdom.  In  this  book,  however,  I  shall  confine  myself 
to  the  latter,  in  the  belief  that  the  truth  of  the  principle 
will  be  granted  in  the  case  of  the  former  as  soon  as  it 
has  been  shown  to  apply  in  that  of  plants. 

The  adoption  of  this  principle  influences  our  attitude 
towards  the  theory  of  descent  by  suggesting  to  us  that 
species  have  arisen  from  one  another  by  a  discontinuous, 
as  opposed  to  a  continuous,  process.  Each  new  unit, 
forming  a  fresh  step  in  this  process,  sharply  and  com- 
pletely separates  the  new  form  as  an  independent  species 
from  that  from  which  it  sprang.  The  new  species  ap- 
pears all  at  once ;  it  originates  from  the  parent  species 
without  any  visible  preparation,  and  without  any  obvious 
series  of  transitional  forms. 


4  Introduction. 

The  Mutation  theoiy  affects  not  only  our  views  on 
the  origin  of  species  but  in  my  opinion  bears  strongly 
on  the  whole  question  of  hybridization.  For  it  shows 
us  that  the  units  with  which  we  deal  in  hybridization  are 
not  the  species  themselves  but  the  single  characters  which 
compose  them — the  so-called  elements  of  the  species. 
This  principle  leads  to  an  entirely  new  method  of  hand- 
ling the  subject,  by  enabling  us  to  proceed  gradually  from 
the  simpler  to  the  more  complicated  phenomena  instead 
of  following  the  present  custom  which  consists  in  dealing 
with  the  complex  cases  first. 

This  work  therefore  falls  into  two  main  parts  of 
which  the  first  treats  of  the  origin  of  species  and  varie- 
ties by  Mutation,  and  the  second  of  the  principles  of 
hybridization. 

The  Mutation  theory  is  opposed  to  that  conception 
of  the  theory  of  selection  which  is  now  prevalent.  Ac- 
cording to  the  latter  view  the  material  for  the  origin 
of  new  species  is  afforded  by  ordinary  or  so-called  in- 
dividual variation.  According  to  the  Mutation  theory 
individual  variation  has  nothing  to  do  with  the  origin 
of  species.  This  form  of  variation,  as  I  hope  to  show, 
cannot  even  by  the  most  rigid  and  sustained  selection  lead 
to  a  genuine  overstepping  of  the  limits  of  the  species 
and  still  less  to  the  origin  of  new  and  constant  char- 
acters. 

Of  course  every  peculiarity  of  an  organism  arises 
from  a  previously  existing  one ;  not  however  by  ordinary 
variation,  but  by  a  sudden  though  minute  change.  It 
is  perhaps  appropriate  to  compare  such  a  change  with 
a  chemical  substitution. 

The  name  I  propose  to  give  to  this  "species-forming" 
variability  is  Mutability — a  term  in  general  use  before 


Introduction.  5 

Darwin's  time.  The  changes  brought  about  by  it,  the 
Mutations,  are  phenomena  as  to  the  exact  nature  of 
which  we  understand  very  httle  so  far.  The  best-known 
examples  of  such  Mutations  are  the  so-called  spontaneous 
variations  (the  "single  variations"  of  Darwin)  by  which 
new  and  distinct  varieties  arise.  They  are  also  termed, 
fitly  enough,  sports.  In  spite  of  the  fact  that  they  occur 
fairly  often,  they  are  usually  not  noticed  until  the  new 
form  has  already  appeared,  when  of  course  it  is  too  late 
to  study  the  phenomenon  of  its  origin  experimentally. 
These  new  forms  can  be  sought  for  in  cultivated  species, 
which  are  seldom  of  pure  origin ;  as  well  as  in  Nature. 
But  as  yet  we  have  no  power  of  inducing  them  at  will. 

It  is  my  belief  that  all  the  simple  characters  of  ani- 
mals and  plants  arise  in  this  way.  . 

The  methods  of  artificial  selection  correspond  to  these 
two  types  of  variability.  Ordinary  variation,  which  is 
also  known  as  individual,  fluctuating  or  gradual  varia- 
tion, is  always  present ;  and  it  can  be  described  in  terms 
of  perfectly  definite  laws  which  have  now  been  fairly 
completely  formulated.  It  provides  the  breeder  with 
material  for  his  improved  races.  On  the  other  hand 
he  has  to  deal  with  Mutations  which  do  not  need  repeated 
selection  but,  at  the  most,  must  be  kept  free  from  ad- 
mixture, and  which  almost  always  breed  true  from  the 
first. 

Under  the  general  term  variation,  then,  are  included 
two  distinct  phenomena :  Mutability  and  fluctuation  or 
ordinary  variation.  The  latter  forms  a  suitable  object 
for  statistical  investigation.  The  epoch-making  re- 
searches of  QuETELET  and  Galton  on  the  anthropo- 
logical side  have  raised  this  study  to  the  position  of  an 
independent  science.     Among  biologists,  Ludwig^  Wel- 


6  Introduction. 

DON,  Bateson,  Duncker,  Johannsen,  Macleod,  and 
others,  have  been  active  workers  in  this  field.  Fluctua- 
tion is  either  individual  or  partial :  in  the  former  case 
we  are  dealing  with  the  statistical  comparison  of  differ- 
ent individuals;  in  the  latter  with  different  but  homolo- 
gous organs  of  the  same  individual;  for  example  with 
the  leaves  of  a  tree.  In  both  cases  the  capacity  for 
variation  is  regarded  by  those  who  are  competent  to 
judge  as  a  means  of  adaptation  to  the  environment. 
Single  organs  vary  partly  in  mass  and  weight  and  partly 
in  number.  The  former  case  is  referred  to  by  Bateson 
as  continuous  variation ;  the  latter  as  discontinuous.  But 
these  terms  are  sometimes  used  by  other  authors  with  a 
different  meaning. 

The  laws  of  Mutability  are  quite  different  from  those 
of  individual  variation;  but,  so  far  as  our  scanty  infor- 
mation reaches  they  are  just  as  independent  of  the  mor- 
phological nature  of  the  mutating  organ.  We  can  dis- 
tinguish between  progressive  and  retrogressive  Mutation. 
The  former  results  in  the  origin  of  a  new  character ;  the 
latter  in  the  loss  of  one  already  existing.  It  is,  obviously, 
to  progressive  Mutation,  according  to  this  theory,  that 
the  main  branches  of  the  animal  and  vegetable  genea- 
logical tree  owe  their  development;  but  the  great  major- 
ity of  the  cases  of  the  departure  of  a  single  species  from 
the  type  of  the  systematic  group  to  which  it  belongs  is 
due  to  retrogressive  Mutation. 

It  is  to  considerations  of  this  kind  that  the  first 
part  of  this  volume  will  be  devoted.  In  the  first  place 
I  shall  give  a  critical  revision  of  the  facts  on  which  the 
theory  of  Natural  Selection  of  Darwin  and  Wallace 
and  others  is  based.  In  the  second  I  shall  deal  with 
some  examples  of  the  experimental  study  of  new  forms. 


Introduction.  7 

The  experiments  to  this  end  were  begun  in  the  autmnn 
of  1886  and  are  now  at  least  in  one  particular  direction 
almost  complete.  A  description  of  them  will  constitute 
most  of  the  contents  of  the  second  part. 

The  critical  revision  to  which  I  have  referred  will 
form  the  substance  of  the  first  section. 

I  shall  confine  my  critique  to  the  facts  of  selection 
and  to  the  material,  afforded  by  variability,  on  which 
selection  operates.  It  will  be  shown  that  artificial  selec- 
tion is,  as  already  mentioned,  a  twofold  process.  On  the 
one  hand  it  consists  in  the  isolation  of  constant  strains 
from  their  neighbors  and,  inasmuch  as  the  best  are  chosen, 
in  their  improvement.  On  the  other  hand  it  improves 
races  and  is  the  source  of  those  superior  fruits  which  we 
can  only  propagate  by  grafting  and  other  vegetative 
methods.  But  this  selection,  so  far  as  our  experience 
goes,  never  leads  to  the  origin  of  new  and  independent 
types. 

In  this  first  section  then  it  will  be  our  object  to 
render  the  difference  between  these  two  types  of  varia- 
bility as  clear  as  possible.  A  correct  apprehension  of  the 
nature  of  this  difference  will  make  clear  the  overwhelm- 
ing importance  of  Mutability,  as  opposed  to  individual 
variation,  in  the  production  of  new  species.  In  connec- 
tion with  this  critical  treatment  I  have  tried,  by  experi- 
ments on  numerous  examples  of  individual  variation,  to 
discover  the  limits  to  the  amount  of  alteration  that  can 
be  attained  in  this  way.  And  we  shall  see  that  these  are 
much  narrower  than  a  belief  in  the  theory  of  Selection, 
as  commonly  entertained,  would  lead  us  to  expect. 

For  the  main  experiment  I  have  chosen  a  plant  in 
which  I  was  enabled  to  follow  in  detail  the  phenomenon 
of   Mutation   through   a   number  of  years.      This   was 


8  Introduction. 

Oenothera  Lamarckiana  which  as  long  ago  as  1886, 
formed  the  starting-point  of  this  work.  The  second 
part  will  show  that  it  has  not  disappointed  me,  and  will 
give  an  account  of  the  whole  series  of  Mutations  pro- 
duced by  it. 


PART  I. 

THE    PRINCIPLES    OF   THE    CURRENT   THEORY    OF 

SELECTION. 


I.  SELECTION  AND  MUTATION. 

In  his  theory  of  Selection  Darwin  combined  two 
principles  relating  to  the  origin  of  species ;  and  he  laid 
stress  sometimes  on  the  one,  and  sometimes  on  the  other, 
according  to  the  nature  of  the  available  evidence  or  to 
the  objections  of  his  critics.  One  was  the  principle  on 
which  the  controversy  over  the  origin  of  species  turned 
in  pre-Darwinian  days.  It  was  the  supposition  of  a 
progress  by  steps  in  nature,  by  means  of  which  a  new 
species  arose  suddenly  from  a  former  one.  Such  a  phe- 
nomenon was  called  a  Mutation.  If  the  new  form  was 
distinguished  from  its  parents  by  a  single  character  the 
mutation  was  obviously  a  relatively  simple  process.  And 
those  who  believed  in  the  "sub-species"  always  regarded 
the  matter  in  this  simple  way,  even  when  they  questioned 
the  possibility  of  such  mutations  on  the  ground  that  they 
never  saw  them.  This  was  the  attitude  of  the  French 
school  in  the  middle  of  the  XlXth  century.  They  rec- 
ognized individual  variation,  and  described  it  time  after 
time;  but  they  saw  no  connection  between  it  and  the 
origin  of  species. 

It  always  seems  an  extraordinary  thing  to  me  that 
the  occurrence  of  mutations  should  have  escaped  the 
notice  of  the  workers  of  that  time.  For  they  occur  both 
in  the  cultivated  state  where  they  have  been  called  single 
variations,  and  also  in  nature,  where  as  I  hope  to  show 

nOFERTT  LIBRARY 

N.  C.  State  College 


12  Selection  and  Mutation. 

they  correspond    precisely   to  the   anticipations   of    the 
Transmutationists  of  that  time. 

The  weak  point  of  the  whole  position  before  Darwin's 
time  lay  in  the  application  of  the  conception  of  mutation 
to  the  Linnean  species,  for  these  are  not  really  elementary 
species  but  aggregate  ones,  and  the  question  of  their 
origin  is  obviously  different  from  that  of  their  con- 
stituent units. 

The  second  principle  in  Darwin's  theory  was  the 
idea  that  individual  variation  could  lead  to  the  origin 
of  new  species  by  continued  selection.  This  idea  was 
at  that  time  absolutely  new,  and  found  many  adherents 
amongst  whom  Wallace,  whose  views  are  set  forth  in 
his  book  ''Darwinism,"  must  be  considered  the  chief. 
Moreover  it  is  Wallace  who  has  insisted  that  this  form 
of  the  theory  affords  the  only  possible  explanation  of 
evolution.  He  absolutely  rejects  the  theory  of  the  origin 
of  species  by  mutation.  ''Single  variations"  according  to 
him  have  no  significance  for  the  theory  of  descent. 

Experimental  researches  on  individual  variability  and 
mutability  hardly  existed  at  all  at  that  time.  Investi- 
gfators  had  to  be  content  with  the  information  of  breeders 
and  general  biological  considerations.  But  the  latter, 
although  they  often  afford  the  .strongest  argument  for 
the  theory  of  descent,  seldom  distinguish  between  the 
two  processes  in  question. 

The  experience  of  breeders  demands  in  my  opinion 
the  most  careful  examination  before  it  can  be  accepted 
as  evidence  in  a  scientific  inquiry.  Their  experiments 
are  neither  designed  nor  carried  out  with  this  object  in 
view.  A  critical  revision  of  the  whole  range  of  facts 
on  which  the  doctrine  of  selection  rests  is  not  only  ad- 
missible, but  is  urgently  called  for.     Darwin  accumu- 


Selection  mid  Mutation.  13 

lated  a  vast  storehouse  of  facts  and  observations;  hut 
our  estimation  of  the  importance  and  significance  of  the 
individual  facts  themselves  has  undergone  a  change. 
Moreover  many  new  observations  have  been  made  which 
place  the  results  obtained  by  breeders  in  a  new  light. 

Breeders  with  few  exceptions  do  not  work  in  the 
service  of  science ;  and  most  of  them  take  very  little  inter- 
est in  the  purely  scientific  aspect  of  their  work.  They  do 
not  make  the  general  plan  of  their  experiments  as  simple 
as  possible  in  the  hope  of  finding  a  rational  explanation. 
On  the  contrary,  as  a  rule,  they  prefer  complex  con- 
ditions especially  where  their  efforts  are  directed  to  the 
production  of  new  varieties.  For  the  more  numerous  the 
factors  the  greater  the  expectation  of  getting  something 
new  and  good.  On  the  other  hand  scientific  experiments 
on  variability  should,  where  possible,  be  free  from  the 
results  of  hybridization.  But  crosses  are  usually  much 
more  important  to  the  breeder  than  pure  races,  and  only 
in  quite  special  cases  has  he  the  occasion  to  exclude 
crossing  with  the  utmost  care.  Although  mutations  are 
often  of  much  greater  value  to  him  than  individual  varia- 
tions he  usuallv  treats  them  both  after  the  same  fashion 
and  often  does  not  even  distinguish  between  them. 

Moreover  a  systematic  record  of  the  culture,  of  the 
kind  that  is  absolutely  essential  to  work  with  a  scientific 
object  is  not  kept  by  breeders.  It  would  cost  far  too 
much  time  and  labor.  The  only  records  that  are  kept 
by  most  breeders  are  those  which  are  necessary  for  the 
compilation  of  their  catalogues.  And  if  after  a  few 
years  a  new  form  proves  to  be  something  particularly 
good,  its  history  is  written,  as  I  have  been  personally  in- 
formed by  one  of  the  most  distinguished  breeders,  partly 
from  the  information  in  the  older  catalogues  and  partly 


14  Selection  and  Mutation. 

from  memory  in  such  a  manner  as  best  suits  the  pur- 
poses of  advertisement.  "It  goes  without  saying,"  he 
said,  ''that  after  three  or  four  years  one  can  no  longer 
remember  one's  single  fertilizations  and  selections." 
Many  other  well-known  breeders  have  expressed  them- 
selves to  me  in  similar  terms.  ^ 

If  we  collect  all  that  is  known  with  absolute  certainty 
about  the  ''How"  of  the  origin  of  our  innumerable 
garden  plants,  the  result  is  extraordinarily  meagre.  Con- 
cerning the  vast  majority  of  them  we  do  not  know  any 
more  than  that  they  exist ;  in  the  case  of  others  the  firm 
which  put  them  on  the  market  is  known,  and  the  year 
of  their  introduction ;  but  the  names  of  their  raisers  are 
usually  kept  secret  especially  where  one  is  dealing  with 
cases  in  which  the  crosses  have  not  been  performed  pur- 
posely. And  the  question  as  to  how  the  new  forms  arose, 
on  the  answer  to  which  the  value  of  this  evidence  as  bear- 
ing on  the  theory  of  selection  depends,  can  very  seldom 
be  answered.  Public  statements  are  dictated  by  exigen- 
cies of  advertisement.  It  is  often  only  found  possible 
to  maintain  a  well-defined  improved  race  on  the  market 
by  crediting  it  with  further  improvement.  All  such 
statements  therefore  require  careful  scrutiny  before  they 
can  be  utilized  as  scientific  evidence. 

I  am  far  from  blaming  breeders  in  this  matter.  It 
is  to  friendly  intercourse  with  many  of  them  that  I  owe 
in  great  measure  my  information  on  this  subject.  What 
I  object  to  is  the  application  by  others  of  the  results  at- 
tained by  breeders  to  questions  for  which  they  were 
neither  intended  nor  devised.     It  was  Darwin's  insight 

^  RiJMKER  refers  in  strong  terms  to  the  difficulties  which  may 
arise  from  regarding  the  grossly  exaggerated  ilhistrations  in  seed 
catalogues  as  faithful  records  of  the  things  depicted.  See  "Der 
zvirthschaftliche  Mehrwerth  guter  Culiurvarietdten,  1898,  p.  2 


Selection  and  Mutation.  15 

which  enabled  him  to  build  his  theory  of  descent  on  foun- 
dations supplied  by  breeders.  At  the  same  time  he  left 
many  points  untouched,  or  at  any  rate  undecided,  and 
for  the  final  settlement  of  such  questions  I  fear  that  the 
statements  of  breeders  will  seldom  suffice. 

It  is  somewhat  remarkable  that  purely  scientific  in- 
vestigation has  not  kept  pace  with  practical  experience. 
This  wide  field  is  still  open  to  cultivation,  and  will,  with- 
out doubt,  some  day  bear  a  rich  harvest. 

It  is  my  object  in  this  section  to  test  the  statements 
of  practical  breeders,  so  far  as  they  admit  of  such  criti- 
cism. I  pay  the  sincerest  tribute  to  their  high  practical 
value  especially  as  in  this  case  science  is  far  behind  them. 
But  their  application  to  the  theory  of  descent  is  another 
matter.  Real  service  to  science  can  only  be  rendered 
by  confining  oneself  to  thoroughly  authenticated  cases. 

In  conclusion  :  The  analogy  between  the  origin  of  new 
forms  in  nature  and  in  a  state  of  cultivation  forms  one 
of  the  chief  supports  of  the  theory  of  descent.  But  the 
fact  of  their  origin  does  not  help  us  to  choose  between 
the  theory  of  selection  and  the  theory  of  mutation ;  noth- 
ing short  of  a  knowledge  of  the  nature  and  mode  of  their 
origin  will  help  us  to  decide.  But  on  this  all-important 
point  the  experience  of  breeders  teaches  us  very  little. 

I  shall  try  to  relate  what  they  tell  us  in  the  third  chap- 
ter of  this  Part. 


11.   MUTABILITY  AND  INDIVIDUAL  VARIA- 
TION. 

§  I.  THE  TRANSMUTATION  THEORY  BEFORE  DARWIN. 

In  the  introduction  to  his  ''Origin  of  Species"  Dar- 
win  erives  a  short  historical   sketch  in  which  he  calls 


Fig.  I.  Papavcr  bracteattim  monopefalum. 
A.  The  detached  Corolla.     B.  The  whole  flower.^ 

attention  to  the  contributions  made  by  his  predecessors 
to  the  theory  of  evolution.    Lamarck  was  the  first  whose 

*  In  the  cultures  of  the  firm  Vilmorin-Andrieux  of  Paris  there 
are  found  every  year  in  the  plots  of  Papaver  bracteatum  single  plants 
whose  petals  are  more  or  less  completely  fused.  Fig.  i  is  drawn 
from  samples  which  H.  L.  de  Vilmorin  was  kind  enough  to  send 


The  Transmutation  Theory  Before  Darwin.       17 

views  on  the  origin  of  species  attracted  general  attention. 
The  chief  of  those  who  joined  him  in  championing  the 
common  origin  of  all  living  form  was  Geoffroy  Saint- 
HiLAiRE.  Their  point  of  view  was  a  purely  philosoph- 
ical one  and  rested  on  the  principles  of  natural  science 
current  at  that  time,  which  sought  to  account  for  all 
natural  phenomena  without  the  aid  of  supernatural  causes. 

Their  followers  however  entered  an  entirely  different 
field.  They  abandoned  for  the  time  the  investigation 
of  the  phylogenetic  relationship  of  all  living  forms  and 
sought  to  discover  the  causes  of  the  relationships  of 
smaller  groups. 

They  adhered  almost  always  to  the  Biblical  concep- 
tion of  creation,  and  sought  to  determine  which  units 
were  created  in  the  beginning.  Some  investigators  re- 
garded the  genera  as  creations,  others  the  species  of 
Linnaeus,  and  a  third  group  the  so-called  ''subspecies" 
which  would  be  much  better  termed  elementary  species. 

There  can  be  distinguished  among  Darwin's  prede- 
cessors and  contemporaries  four  different  lines  of  thought 
characterized  by  their  different  attitudes  to  Darwin's 
theory  of  descent. 

1.  The  philosophical  contemplation  of  nature  by  La- 
marck and  Geoffroy   Saint-Hilaire. 

2.  The  rest  of  the  Transmutationists  who  regarded 
the  genera  as  created  and  the  species  and  subspecies 
as  derived  from  these. 

3.  The  adherents  of  the  Linnean  species,  who  held 
that  these  were  created. 

4.  The  so-called  school  of  Jordan  who  declared  that 

rne.  The  plant  is  not  on  the  market.  It  is  not  unreasonable  to  be- 
lieve that  the  appearance  of  the  first  ancestor  of  the  whole  systematic 
division  of  the  Sympetalae  occurred  in  geological  time  in  the  same 
way  as  sympetaly  has  arisen  here  as  a  variety. 


18  Mutability  and  Individual  Variation. 

the  elementary  forms  which  proved  themselves  immu- 
table when  cultivated  were  the  real  independent  creations. 

Let  us  first  consider  the  views  of  the  Transmutation- 
ists. 

Before  Linnaeus  the  genera  were  regarded  as  the 
systematic  units  and  the  species  were  considered  as  sub- 
divisions of  them.  Many  genera  have  popular  names : 
these  groups  were  known  by  the  country  folk,  whilst 
the  species  were  only  in  much  rarer  cases  distinguished. 
TouRNEFORT  gave  the  genera  known  to  him  their  sys- 
tematic names ;  but  the  species  he  distinguished  only  by 
symbols  and  not  by  special  names.  In  his  eyes  the 
genera  were  the  essential  things,  the  species  merely  de- 
rivatives. 

The  view  that  genera  were  created  in  the  beginning 
and  that  species  had  developed  from  them  in  the  lapse 
of  time  by  transmutation  had  many  adherents.  Among 
them  are  to  be  reckoned  Buffon,  at  least  in  his  earlier 
works,  then  Bory  de  Saint- Vincent,  Gmelin,  Bur- 
DACH,  PoiRET,  Fries  and  many  others.^  This  view,  at 
one  time  found  an  adherent  in  Linnaeus.^  He  believed 
in  a  simultaneous  creation  of  all  forms  in  Paradise ;  he 
suspected  however  that  these  forms  corresponded  to  our 
genera  whilst  species  had  arisen  from  them  in  part  di- 
rectly and  in  part  by  crossings.*^ 

This  is  important  because  it  shows  that  the  modern 
conception  of  species  did  not  exist  before  the  time  of 
Linnaeus  or  at  any  rate  that  it  was  not  the  species  which 

^  GoDRON,  De  I'Espccc,  pp.  8-10. 

^  "Genus  omne  est  nafurale,  in  primordio  tale  creatum."  Syst. 
Nat.  Veg.  14.    Philos.  Bot.  No.  159,  p.  104. 

C.  LiNNE,  Oratio  de  Telluris  hahitabilis  incremento.  Upsala, 
1743;  Leyden,  1744. — Idem  Amocnitatcs  academicac.  1794.  T.  I., 
p.  71  {de  Peloriis). 


The  Transiimtation  Theory  Before  Darwin.       19 

were  regarded  as  the  real  units  of  the  system.  This  is 
also  obvious  from  the  meaning  of  the  expression  noinen 
specificiim  which  was  in  use  at  that  time.  Tournefort 
and  his  contemporaries  wrote  after  the  generic  name  a 
short  diagnosis  each  time,  in  order  to  distinguish  the 
single  species  from  one  another.  So  long  as  only  a  few 
species  were  known  in  each  genus,  one  character  sufficed. 
But  as  the  number  of  species  increased  more  characters 
became  necessary,  until  finally  many  species  could  only 
be  denoted  by  a  description  which  occupied  several  lines. 
A  circumlocution  of  this  kind  we  now  call  a  diagnosis; 
then  it  was  called  a  nomen  specificimi  and  had  to  be 
written  out  every  time  one  wanted  to  refer  to  a  particular 
species. 

LiNNAEU's  substituted  his  binary  nomenclature  for 
these  cumbersome  noniina  specifica^  and,  in  order  to 
give  his  species  the  necessary  importance  he  raised  them 
to  the  rank  of  the  units  of  the  system.  He  advanced 
the  proposition  Species  tot  numeramns,  qiiod  diversae 
formae  in  principio  sunt  creatae^  and  thus  laid  the  foun- 
dation of  the  conception  of  species  that  is  recognized 
to-day.  And  just  as  it  had  been  supposed  up  to  that 
time  that  species  arose  from  genera  by  natural  means, 
so,  according  to  Linnaeus,  smaller  types  had  arisen 
from  the  species.^  But  in  order  to  insure  as  far  as  pos- 
sible the  supernatural  dignity  of  his  species  Linnaeus 
forbade  his  students  to  study  the  smaller  types :  Varie- 
tates  lez'issinias  non  curat  botanicus,  ran  the  command."* 

LiNNAEUs's  species  were  aggregate  species  and  not 

^  Philosophia  Botanica,  No.  257,  p.  207. 

'  Ibid.,  No.  157,  p.  103. 

^  "Varietates  sunt  plantae  eiusdem  specie!,  mutatae  a  caiissa  qiia- 
CLinque  occasionali,"  Ibid.,  No.  306,  p.  243 ;  No.  158,  p.  104. 

*  Ibid.,  No.  310. 


20 


MiLtahility  and  Individual  Variation. 


true  units.  It  seems  that  Linnaeus  himself  was  fully 
aware  of  the  fact,  but  it  is  certain  that  it  was  gradually 
lost  sight  of  by  his  followers.  In  relatively  few  cases 
did  he  himself  distinguish  varieties  within  his  species, 
and  it  is  well  known  that  when  he  did  they  were  often 
raised  to  the  rank  of  species  by  those  who  followed  him. 
Well-known  examples  are  afforded  by  Primida  veris  L. 

with  the  three  varieties  vid- 
garis  (acaulis)  (Fig.  2),  cla- 
tior  and  officinalis ^  which 
are  now  universally  re- 
garded as  species  solely  on 
the  authority  of  Jacquin 
without  any  further  justi- 
fication. In  like  manner 
Lychnis  dioica  L.  split  up 
into  L.  diiirna  and  L.  vcs- 
pcrtina,  Platanthcra  bifolia 
L.  into  P.  bifolia  and  P. 
chlorantha  and  so  forth. 

Numerous  examples  of  a 

similar    kind    will    occur    to 

the  reader.     Conversely  also  Linnean  species  have  been 

degraded  to  the  rank  of  varieties :  for  example  the  Index 

Kewensis  which  recognizes  the  Primula  species  of  Jac- 

^  Primula  acaulis  is  distinguished  from  the  two  other  subspecies 
by  the  fact  that  its  flowers  arise  singly  by  their  stalks  from  the  axils 
of  the  leaves  and  are  not  united  to  form  an  umbel.  This  species 
occurs  in  certain  localities  in  the  Netherlands,  in  the  wild  state,  and 
from  time  to  time  bears  umbels  of  which  one  is  drawn  in  Fig.  2. 
Such  cases  are  regarded  as  atavistic,  as  reversionary  to  some  common 
ancestor  of  those  Primulas  which  still  possess  umbels.  But  this  atav- 
ism is  not  considered  by  the  best  systematists  as  sufficient  ground  for 
re-constituting  P.  acaulis  as  a  variety  and  the  main  species  P.  veris  as 
a  species,  in  systematic  works.  From  the  point  of  view  of  the  estima- 
tion of  the  systematic  value  of  Atavism  in  general  this  case  evidently 
is  of  much  importance. 


Fig.  2. 


An  umbel  of  Primula 
acaulis. 


The  Transmutation  Theory  Before  Darwin.       21 

QUiN  regards  Datura  Tatula  L.  as  a  variety  of  D.  Stra- 
monium L.^ 

Linnaeus^  species,  therefore,  embraced  his  varieties 
and  these  varietates  minores,  which  he  would  not  allow 
his  pupils  to  investigate.  But  it  was  not  proved  that  all 
these  smaller  types  had  arisen  from  the  species ;  it  merely 
followed  from  his  definition  of  species.  And  so  long  as 
the  Linnean  species  of  the  systematists  provided  them 
with  sufficient  work  there  was  no  reason  for  them  to 
doubt  his  words  or  disregard  his  precept.  But  as  the 
study  and  description  of  the  "species"  particularly  of  the 
European  Flora  gradually  approached  completion  the 
attention  of  naturalists  inevitably  turned  in  the  direction 
of  the  hitherto  neglected  Varietates  minores. 

It  soon  became  evident  that  these  were  much  more 
numerous  than  Linnaeus  ever  supposed ;  moreover,  that 
they  were  distinguished  by  just  as  numerous  and  just 
as  definite  characters  as  Linnean  species.  Their  discov- 
erers demanded  for  them  the  ''rank"  of  Linnean  species 
and  elevated  them  to  it.  Some  authors  went  so  far  as 
to  assert  that  by  such  discriminations  they  had  created 
new  species. 

The  best  known  example  is  afforded  by  Draba  verna 
which  has  been  studied  carefully  by  Jordan  and  by  many 
other  independent  investigators  after  him.  Among  the 
latter  I  would  mention  De  Bary  whose  results,  which 
are  in  full  agreement  with  Jordan's  were  published  after 
his  death,  by  F.  Rosen  in  the  Botanische  Zeitung  for 
1S89.  The  European  Flora  includes  about  200  (elemen- 
tary) "species"  of  Draba  which  together  constitute  the 
old  species   Verna  and,  so  far,  have  remained  constant 

^  It  is  most  remarkable  that  in  the  Index  Kewensis  which  was 
published  at  Darwin's  expense  after  his  death  no  distinction  is 
drawn  between  varieties  and  synonyms. 


22 


Mutability  and  Individual  Variation. 


and  distinct  under  cultivation.  The  extent  of  these  dif- 
ferences is  sufficiently  indicated  by  a  series  of  the  most 
important  forms,  in  Fig.  3. 

A  heated  controversy  in  which  Jordan  and  Godron 
played  the  most  prominent  parts  has  raged  over  the  ques- 


Fig.  3.  Subspecies  of  Draba  verna.  i.  D.  violacea ;  2.,  3. 
and  4.  D.  scabra;  5.  D.  subnitens ;  6.  D.  majuscula  ;  7.  D. 
obconica  ;  8.  D.  glaucina  \  9.  D.  clongata  ;  10.  D.  graminea. 
(After  F.  Rosen,  Bot.  Zeitung,  1889.  Plate  VIII.) 

tion  as  to  whether  these  smaller  perfectly  circumscribed 
types  should  be  called  species  or  not.  Jordan  and  the 
advocates  of  the  smaller  species  based  their  views  on 
the  results  of  cultures ;  and  in  this  way  they  have  en- 


The  Transmutation  Theory  Before  Darwin.       23 


riched  science  with  a  collection  of  experimental  facts  of 
the  greatest  importance.  A  considerable  portion  of  the 
fourth  chapter  of  this  work  will  be  devoted  to  a  critical 
consideration  of  these  facts. 


Fig.  4.  Subspecies  of  Viola  tricolor.  j.V.agrestis',  2.V. 
segetalis,  general  habit  similar  to  that  of  I',  agrestis ;  3. 
V.  gracilescens;  4.  V.  pallescens ;  5.  V.  nemausensis. 
(After  A.  Jordan,  Observ.  s.  plusicurs  plantes  rares  ou 
critiques,  II,  1846.     Plates  i  and  2.) 

The  description  of  any  form  as  a  species,  or  rather 
the  supposed  proof  that  any  form  zvas  a  species,  carried 


24  Mutability  and  Individual  Variation. 

with  it  the  assumption  that  the  form  under  consideration 
had  been  created  as  such.  The  reasonableness  of  this 
position  was  recognized  by  both  parties  but  especially 
by  GoDRON  and  Jordan.  But  at  the  present  day  when 
the  common  origin  of  all  species  is  hardly  ever  called  in 
question  it  is  very  difficult  to  judge  this  controversy  fairly. 

The  origin  of  a  new  form  from  another  was  termed 
at  that  time  a  mutation.^  Godron  and  Jordan  asserted 
that  every  one  of  the  forms  constituting  their  species  was 
immutable.  Jordan  moreover  tried  to  prove  the  truth 
of  this  statement  by  breeding  experiments.  He  recog- 
nized individual  variation  and  observed  and  recorded  it 
accurately.-  He  was  also  acquainted  with  local  races^ 
whose  differences  disappear  whenever  they  are  cultivated 
for  a  few  years  next  one  another  in  the  same  soil ;  he 
knew  moreover  that  as  a  rule  it  took  only  a  few  genera- 
tions to  effect  this  change.  Further,  he  was  familiar 
with  the  results  of  accidental  crosses  by  insects  or  wind, 
and  mentioned  the  genera  {Cirsiiim  etc.)  in  which  this 
was  most  apt  to  occur. 

But  individual  variability  and  mutability  were  abso- 
lutely different  things  in  his  eyes ;  he  frequently  observed 
the  first;  but  never  saw  an  example^  of  the  latter.  That 
was  why  he  held  species  to  be  immutable.^"* 

^  Already  Lamarck  used  the  terms  "races  muiahlcs  on  variables" ; 
see  GiARD,  Discours  d'ouverturc  de  J.  B.  Lamarck,  1907,  page  iii 
(Note  of  1908). 

^A.  Jordan,  De  I'origine  dcs  arbrcs  fniiticrs,  1853,  p.  9. 

^  Loc.  cit.,  p.  10 

*  Besides  the  common  Viola  tricolor,  V.  arvensis  (Murray)  is 
very  familiar;  it  is  reckoned  by  many  authors  as  belonging  to  the 
same  species.  Compare  for  example  Koch,  Synopsis  Florae  ger- 
manicac  et  hclveticae.  V.  arvensis  itself  consists  of  a  series  of  con- 
stant forms  of  which  our  Fig.  4  shows  some  of  the  more  important. 

^Jordan,  De  VOrigine  des  arbres  fruifiers,  1853.  Tn  this  work 
and  in  the  other  essays  Jordan  always  uses  the  words  "niufation" 
and  "inimutabilite"  where  he  is  dealing  with  the  supposed  change  of 


nftFERU  LIBRART 
fl.  C.  State  College 


The  Transimitation  Theory  Before  Darwin.       25 

GoDRON  also  distinguishes  quite  clearly  between  spe- 
cific characters,  and  trivial  fortuitous  and  purely  ''indi- 
vidual" deviations  which  soon  disappear  when  the  condi- 
tions wdiich  called  them  forth  cease.  The  latter  are  united 
together  by  a  series  of  transitions;  the  former  are  not.-' 

When  Darwin's  work  on  the  origin  of  species  ap- 
peared,^ the  controversy  over  the  ideas  of  species  and 
mutability  raged  most  fiercely  in  France.  But  it  only 
turned  on  the  question  whether  the  larger  or  the  smaller 
species  were  separately  created,  or  whether  they  had  both 
arisen  from  an  original  type.  This  original  type,  how- 
ever, was  never  thought  of  as  being  larger  than  a  genus. '^ 
The  transformation  or  transmutation  theory  of  those 
days  was  therefore  an  entirely  different  thing  from  the 
modern  theory  of  descent.  Nevertheless  Darw^in  him- 
self says  in  1858  at  the  suggestion  of  Lyell  and  Hooker 
he  resolved  to  write  a  book  on  the  ^'Transmutation"  of 
species,  a  book  which  was  published  in  the  following 
year  under  the  title  of  the  Origin  of  Species.^ 

It  is  curious  that  the  terms  Mutation,  Mutability,  Im- 
mutability and  so  forth  should  have  been  so  completely 
driven  out  of  use  by  the  theory  of  Selection.  Darwin 
directed  his  whole  energy  wnth  full  knowledge  against 
the  dogma  of  the  immutability  of  species.  His  ''Origin 
of  Species"  begins  with  the  statement  that  until  recently 
the  great  majority  of  investigators  had  believed  "that 
species  were  immutable  productions."'^  "I  had  become, 
in  the  year  1837  or  1838,  convinced  that  species  were 
mutable  productions,"^   says  he  in  his  Autobiography; 

one  species  into  another.     See  pp.  7,  g,  ii,  13,  34,  etc.    Also  Godron, 
De  I  Espcce,  e.  g.,  II,  p.  422. 

^Godron,  De  l' Espcce,  I,  p.  175.  ^  Nov.  24,  1859. 

^  See  Wallace,  Darzvinism,  pp.  3-6.      *  Life  and  Letters,  T.  p.  85. 

^Origin  of  Species,  6th  ed.,  1898.     Historical  Sketch,  p.  xiii. 

^  Life  and  Letters,  I,  p.  93. 


26  Mutability  and  hidividual  Variation, 

and  in  the  passage  cited  in  the  Origin,  he  discusses  the 
question  whether  in  Paleontology  the  immutability  of 
species  was  or  was  not  assumed  by  the  most  prominent 
workers.-^ 

The  prevailing  opinion  was  that  individual  variability 
and  mutability  were  two  distinct  phenomena.  Variabil- 
ity was  well  known  both  in  cultivated  and  in  wild  species, 
but  most  thoroughly  in  wild  species  which  had  been  kept 
in  cultivation  through  a  number  of  years.  It  was  found 
however  to  be  limited,  to  depend  upon  the  influence  of  the 
environment  and  to  be  useful  as  a  means  of  adaptation. 
Mutability  was  not  encountered  in  practical  experience. 
No  cases  of  a  species  arising  from  another  had  occurred  in 
scientific  cultures,  nor  were  there  any  sufficiently  authenti- 
cated instances  of  the  origin  of  new  forms  in  the  nursery 
or  the  farm  in  spite  of  a  thorough  and  critical  scrutiny.^ 

The  adherents  of  the  Transmutation  theory  explained 
the  systematic  relationship  of  the  single  forms  (species, 
varieties,  and  so  forth)  within  the  genera  by  the  theory 
that  they  had  a  common  origin.  The  opponents  of  this 
theory,  in  so  far  as  they  were  upholders  of  the  Linnean 
conception  of  species,  held  exactly  the  same  views,  except 
that  they  regarded  the  species  as  created  and  not  the 
genera.  Foremost  amongst  them  was  Godron.  who  con- 
sidered the  races  and  varieties  and  even  the  species  of 
Jordan  as  having  arisen  from  the  Linnean  species  by 
natural  means,  and  made  a  very  extensive  collection  of 
facts  and  observations  to  prove  this  view. 

The  third  school  was  sharply  opposed  to  these  two 
groups,  the  Transmutationists  and  the  upholders  of  the 

^  Origin,  p.  xviii. 

^Jordan,  De  VOriginc  des  arhres  fruiticrs,  1853,  and  Godron,  De 
I'cspcce  et  des  races. 


The  Transmutation  Theory  Before  Darwin.       27 

Linnean  conception  of  species.  It  relied  exclusively  on 
the  Biblical  story  of  creation  and  on  experiment.  Every 
form  which  proved  itself  to  be  immutable  by  experiment 
was,  according  to  their  theory,  an  independently  created 
form.  The  experiment  consisted  in  cultivating  the  par- 
ticular form  in  a  garden  for  a  few  generations.  They 
disapproved  of  the  systematic  grouping  together  of  such 
pure  forms  into  larger  "species"  on  the  ground  that  it 
was  artificial  and  arbitrary.  They  recognized  genera 
and  the  larger  groups  as  necessary,  but  regarded  them 
as  manifestly  artificial  divisions. 

According  as  one  belonged  to  the  one  or  the  other 
of  these  parties  one  was  more  or  less  prepared  for  Bar- 
wind's  new  teaching.  The  thin  ranks  of  the  Transmuta- 
tionists  and  the  huge  Linnean  army  admitted  a  priori  the 
origin  of  races,  varieties  and  Jordan^s  species  from  other 
forms,  and  this  in  spite  of  the  complete  absence  of  ex- 
perimental proof.  It  was  against  these  that  Darwin 
turned  his  energies  to  show,  what  was  indeed  the  chief 
object  of  his  argument,  that  the  supposition  of  a  com- 
mon origin  for  genera  and  families  was  as  much  justified 
as  the  view  held  at  that  time,  that  the  forms  gathered  to- 
gether in  one  species  were  descended  from  a  common 
ancestor. 

The  adherents  of  Jordan^s  school  who  regarded  the 
elementary  species  as  created,  were  least  prepared  for 
Darwin^s  teaching.  There  were  however  very  few  of 
them,  and  their  system,  by  being  so  rich  in  species  (Draba 
verna  alone  falls  into  more  than  200),  stood  very  much 
in  the  way  of  a  wide  acceptance  of  their  views.  At  any 
rate  they  were  not,  or  at  most  only  very  slightly,  con- 
vinced by  Darwin  ;  the  bulk  of  them  maintained  their 
original  position.     The  only  one  of  them  that  I  would 


28  Mutability  and  Individual  Variation. 

mention  here  is  Michaele  Gandoger  whose  Flora  Eu- 
ropae  is  the  most  comprehensive  work  along  this  line  of 
research. 

The  controversy  before  the  time  of  Darwin  had 
therefore  led  to  two  essentially  distinct  results.  These 
were : 

1.  The  experimental  proof  of  the  existence  of  nu- 
merous, constant  and  mutually  independent  types  within 
the  limits  of  the  Linnean  species. 

2.  The  general  conviction  that  these  constant  types 
had  arisen  naturally  from  larger  groups  or  species  by 
mutation.  ^ 

§  2.  DARWIN'S  SELECTION  THEORY. 

The  theory  of  Descent  aims  at  the  scientific  explana- 
tion of  systematic  relationship.  It  is  Darwin's  immortal 
service  to  have  obtained  general  recognition  for  this 
generalization.  By  doing  this  he  revolutionized  the 
whole  of  biological,  systematic,  embryological  and  pale- 
ontological  science,  tapping  inexhaustible  sources  for  new 
investigation  and  discovering  everywhere  mines  where 
new  facts  wxre  to  be  had  for  the  picking  up. 

The  several  propositions  and  hypotheses  which  Dar- 
win employed  as  supports  for  this  theory  should  be  re- 
garded now  only  as  such,  since  their  interest  is  mainly 
historical.  They  have  served  their  purpose  and  are 
thereby  fully  justified.  Whether  they  contain  in  part 
what  is  unproven  or  what  is  incorrect  matters  not.  But 
they  contain,  over  and  above  that,  a  large  mass  of  im- 
portant facts  which  can  be  made  use  of  to  build  further 

*  The  terms  immutability  and  so  forth  have  not  entirely  dropped 
out  of  use.  E.  g.,  B.  J.  Costantin,  Accomodation  dcs  plantes  aux 
cliniats  froid  et  chaud,  Bull.  Scientif., public  par  Alfred  Giard,  T.  31, 
p.  490,  1897,  and  Bateson,  Materials  for  the  Study  of  Variation, 
1894,  P-  2. 


Darzmn's  Selection  Theory.  29 

on  the  foundations  laid  by  Darwin.  This  is  especially 
true  of  the  theory  of  selection,  which  now  has  served  its 
time  as  an  argument  for  the  theory  of  Descent;  happily 
this  theory  no  longer  stands  in  need  of  such  support. 
We  are  now  concerned  to  bring  the  origin  of  species  into 
the  field  of  experimental  investigation.  The  position 
of  the  theory  of  Descent  as  a  comparative  science  is  com- 
pletely assured  by  the  results  Darwin  obtained ;  but  as 
an  experimental  science  it  has  made  feeble  progress.^ 

The  cause  of  this  lies  in  my  opinion  not  so  much  in 
the  difficulties  of  the  investigation  as  in  the  lack  of 
definiteness  of  this  part  of  the  theory.  In  the  systematic 
sphere  the  discoveries  could  have  been  predicted ;  this 
was  far  from  being  the  case  on  the  physiological  side. 

Darwin  was  never  quite  clear  about  the  physiolog- 
ical part  of  the  theory  of  Selection.  It  seems  to  me 
that  he  always  inclined  first  in  one  direction  and  then 
in  another,  never  fully  deciding  between  the  two  views. 
In  his  earlier  works  especially,  he  treated  spontaneous 
variations  (single  variations)  as  the  material  afforded 
for  natural  selection  whilst  in  his  later  works,  in  con- 
sequence of  the  objections  of  his  critics  he  gave  greater 
prominence  to  the  part  played  by  individual  variation  in 
the  production  of  new  species.  But  he  never  sharply  dis- 
criminated between  these  two  processes.  Moreover,  such 
a  discrimination  was  not  in  the  interests  of  his  main  ob- 
ject. It  would  have  led  him  to  many  difficult  points  whose 
solution  was  not  necessary  to  the  theory  of  descent,  and 
would  have  diverted  attention  too  much  from  the  main 
point  at  issue. 

As    we    have    seen    in    the    foregoing    section,    the 

*  See  also  Bateson^  Materials  for  the  Study  of  Variation,  pp.  7 
and  II. 


30  Mutability  and  Indiz'idiial  Variation. 

proposition  that  races,  varieties  and  subspecies  of  wild 
as  well  as  of  cultivated  plants  have  arisen  by  certain 
modifications  from  "species"  received  general  recogni- 
tion. Darwin  had  collected  all  the  facts  available  for  a 
history  of  these  changes  in  the  case  of  cultivated  plants.^ 
They  provide  us  with  a  history  of  garden  plants  and 
often  also  give  the  source  and  the  date  of  introduction 
of  varieties,  but  they  do  not  tell  us  whence  they  came 
or  how  they  arose.- 

^'Varieties  arc  incipient  species"  and  ''species  have 
descended,  like  varieties,  from  other  species" ;  these  are 
the  two  famous  propositions  which  Darwin  is  contin- 
ually asserting  and  with  whose  proof  he  is  chiefly  con- 
cerned.^ In  other  words:  the  origin  of  varieties  from 
species  is  granted ;  why  not  species  from  species  ?  In 
order  to  prove  this  it  is  obviously  not  necessary  to  know 
the  exact  way  in  which  varieties  themselves  originate. 
It  is  sufficient  tliat  the  relation  between  species  and 
genera  is  the  same  as  that  between  varieties  and  species. 

Darwin  asserts  again  and  again  that  it  must  not  be 
forgotten  that  under  the  term  of  variations  mere  indi- 
vidual differences  are  included.^  His  variabilitv  is  there- 
fore  always  to  be  understood  in  a  double  sense.  It  con- 
sists on  the  one  hand  of  individual  difi^erences  and  on 
the  other  of  single  variations.'^  The  former  belong  to 
those  phenomena  which  we  now  term  individual  varia- 

^  Of  later  works  compare  especiallj'  Alph.  de  Candolle^  Suv 
Vorigine  dcs  plantes  cultivccs. 

^  See  also  Bateson,  Materials,  p.  17. 

^  Origin  of  Species,  6th  ed.,  pp.  2,  4,  86,  etc. 

*  Origin,  ibid.,  pp.  64,  80,  etc. 

^ Life  and  Letters,  III,  p.  108.  As  examples  of  single  variations 
are  considered  such  cases  as  the  color  of  the  flowers  of  Datura  Tatula 
(a  blue  form  belonging  to  the  white-flowered  D.  Strainoniiim)  and 
the  absence  of  spikes  on  the  fruits  of  Datura  mcrmis.     See  Fig.  5. 


Darwin's  Selection  Theory. 


31 


tion,  and  conform  to  Ouetelet's  law.  The  latter  are 
sporadic,  spontaneous  changes  corresponding  to  our  Mu- 
tations (Fig.  5). 

Darwin  almost  always  speaks  of  these  two  types  in 
his  discussion  on  Selection  but  never  separates  them, 
and  is  always  in  doubt  as  to  their  relative  importance 
in  the  origin  of  species. 


Fig.  5.  I.  Datura  Tatula,  with  blue  corolla  and  fo- 
liage tinged  with  red.  2.  Fruit  of  D.  Stramo- 
nium with  thorns,  unripe.  3.  Fruit  of  D.  (Straiiw- 
niuui)  inennisj  without  thorns,  ripe,  dry  and  open. 

This  being  the  case,  it  seems  to  me  that  it  is  almost 
unfair  in  a  criticism  of  Darwin^s  views  to  regard  these 
two  types  as  distinct.  If  I  do  so,  I  do  it  with  the  express 
object  of  showing  that  although  Darwin  was  acquainted 
with  the  two  phenomena  he  was  not  prepared  to  separate 
them  completely  on  the  basis  of  their  significance  for 


32  Mutability  and  Individual  Variation. 

his  theory.  Here,  as  everywhere,  Darwin  advanced 
with  the  utmost  caution. 

Our  problem  then  is  this :  In  the  formation  of  new 
species,  does  natural  selection  choose  the  extreme  vari- 
ants of  the  ordinary  individual  variation,  or  does  it  choose 
occasional  Mutations.  In  any  large  community  there  is 
always  an  abundant  supply  of  extreme  variants.  More- 
over the  struggle  for  existence  does  not  preserve  the 
single  absolutely  perfect  ones  only,  but  groups  of  the 
best,  since  it  simply  eliminates  the  least  perfectly  adapted. 
There  is,  so  to  speak,  always  plenty  of  material  for  se- 
lection in  every  species,  and  in  every  character.  But  in- 
dividual variability  is,  as  far  as  our  experience  goes,  by 
no  means  unlimited ;  its  limits  are  not  indeed  precise,  but 
thev  fall  well  within  the  rano-e  of  Ouetelet's  Law. 

Single  variations  are  chance  phenomena  into  whose 
essential  nature  Ave  have  as  yet  no  insight.  We  know 
that  they  occur  and  that  they  occur  seldom ;  but  not  too 
seldom.  As  to  how  they  come  about  scarcely  anything 
is  known,  but  it  is  generally  assumed  that  they  appear 
suddenly,^  and  they  are  consequently  termed  sports.  They 
suddenly  change  a  species  into  a  new  form ;  or,  from  a 
variety,  they  make  a  new  one  absolutely  different.  Fre- 
quently they  concern  only  a  single  character  and  then 
usually  consist  in  the  loss  or  latency  of  a  character  al- 
ready present,  e.  g.,  white  flowers,  absence  of  thorns 
{Datura  incrmis,  Fig.  5),  hairs,  runners  (e.g.,  Fragaria 
alpina,  Figs.  6  and  7,  pp.  33  and  34),^  seeds,  branching, 

^  By  far  the  majority  of  observations  that  have  been  adduced  as 
instances  come  under  the  heading  of  hybridization. 

^The  Gaillon  strawberries  (Fig.  7)  which  are  distinguished 
from  the  ordinary  monthly  strawberries  (Fragaria  alpina,  Fig.  o; 
solely  by  the  absence  of  suckers  and  the  correspondingly  greater 
branching  of  the  rosettes  are  often  cultivated  for  the  very  reason  of 


Darwin's  Selection  Theory.  Z2> 

etc. ;  these  cases  are  instances  of  retrogressive  mutability 
and  have  no  signification  for  the  elucidation  of  the  main 
lines  of  descent. 

Apart  from  this  quite  definite  group  of  modifications 
hy  loss,  single  variations  seem  to  be  presented  by  all  char- 
acters, to  proceed  in  every  direction  and  to  be  apparently 
without  limit.  To  sum  up,  individual  differences  are  al- 
ways present,  occur  in  every  direction  and  in  every  char- 
acter, but  are  limited  and  conform  to  definite  laws.  Single 
variations,  on  the  other  hand,  are  sporadic  phenomena, 
appearing  only  from  time  to  time,  and  suddenly  changing 


Fig.  6.    Fragaria  alpina,  IMonthly  Strawberry. 
(Fraisier  des  quatre  saisons.) 

the  forms  of  life.     They  cannot  be  induced  at  will,  but 
must  be  waited  for.^ 

We  have  thus  to  decide  between : 

1.  a  selection  of  extreme  variants. 

2.  a  selection  of  mutants. 

The  question  for  Darwin  was.  which  of  these  two 
has  played  the  greater  part  in  the  origin  of  species  ?- 

this  deficienc3^   See  Vilmorin-Andrieux,  Les  plantes  potageres,  1883, 
pp.  221-222. 

^  Origin,  loc.  cit.,  p.  62. 

^  The  selection  of  extreme  variants  in  nature  forms  the  so-called 
local  races  and  plays  an  important  part  not  only  in  acclimatization 
but  especially  in  many  cases  of  adaptation  to  new  environmental  con- 
ditions.    See  III,  §  4. 


34 


Mutability  and  Individual  Variation. 


The  breeder  employs  both,  according  as  opportunity 
offers.  Darwin  asserts  over  and  over  again  that  their 
method  consists  in  the  accumulation  of  successive  slight 
variations.^  But  as  to  whether  these  small  changes  are 
variations  or  mutations  he  gives  no  decision.  Natural 
selection,  he  says,  like  artificial,  chooses  these  ''slight 
variations,''^  but  to  which  category  these  severally  be- 
long is  left  uncertain.  Moreover  it  was  Darwin's  belief 
that  Natural  Selection  was  not  the  sole  factor,  for  at  the 


Fig.  7.  Fragaria  alpina,  Monthly  Strawberry  with- 
out runners.  (Fraisier  des  quatre  saisons  sans 
coulants,  Fraisier  de  Gaillon). 

conclusion  of  the  introduction  to  his  Origin  he  says,  '7 

am  convinced  that  natural  selection  has  been  the  most 

important,  but  not  the  exclusive  means  of  modification.'"^ 

In  almost  all  works  on  Darwin's  theory  we  find  the 

.story  of  how  he  arrived  at  his  theory  of  selection  by 

reading  Malthus's  Essay  on  Population."*    Already  well 

^  Origin,  loc.  cit.,  pp.  3,  63,  64,  etc. 

'  Ibid. 

^  See  also  Origin,  p.  72. 

*  See  Life  and  Letters,  I,  pp.  83,  84. 


Darwin's  Selection  Theory.  35 

acquainted  with  the  struggle  for  existence  and  the  un- 
ceasing destruction  of  countless  individuals,  he  found  in 
that  book  the  long  sought  solution.  He  came  to  the  con- 
clusion that  selection  played  the  same  part  among  animals 
and  plants  as  it  does  amongst  mankind,  and  that  in  this 
manner  species  may  have  arisen.  This  conclusion,  how- 
ever, is  simply  the  idea  of  a  genius  and  does  not  directly 
follow  from  Malthus's  work.  It  has  become  one  of 
the  main  supports  of  the  doctrine  of  descent.  But  it 
was  to  the  genius  of  the  great  thinker,  not  to  the  sound- 
ness of  the  raw  material  that  the  magnificence  of  the 
result  was  due. 

'  In  the  light  of  what  we  know  now^  this  story  of  the 
origin  of  the  theory  of  selection  often  stands  openly 
contradicted  by  Darwin^s  own  view.  Natural  selection, 
says  he,  works  on  ''chance  variations''^  ''Unless  such 
occur  natural  selection  can  do  nothing.''^  From  such 
utterances  it  is  clear  that  Darwin  attributed  a  very  great 
and  often  preponderating,  perhaps  even  an  exclusive, 
significance  to  "single  variations/'  For  individual  varia- 
bility always  provides  natural  selection  with  the  required 
material  in  the  form,  sometimes  of  greater  and  some- 
times of  less  deviations  from  the  type;  it  is,  moreover, 
exhibited  everywhere  and  in  all  directions.  This  fact 
was  known  quite  well  at  that  time,  and  Darwin  himself 
was  quite  clear  about  it.  But  the  laws  formulated  later 
bv  OuETELET  wcrc  not  known ;  and  the  p'eneral  insidit 
into  the  matter  was  much  less  deep  than  it  is  at  present ; 
no  one  however  questioned  the  universal  occurrence  of 

*  It  was  in  1838  that  Darwin  read  Malthus's  book,  and  Quete- 
let's  Anthropomctvie  first  appeared  in  1870. 

^  Life  and  Letters,  II,  p.  87,  etc. 

^  Origin,  p.  64,  etc. 


36  Mutability  and  Individual  Variation. 

variability.  The  chance  variations  were  not  therefore 
the  extreme  variants  of  the  ordinary  variabiHty;  they 
were  sporadic  occurrences.  Natural  selection  is  on  the 
lookout  for  these,  says  Darwin,  and  seizes  on  them 
^'whenever  and  wherever  opportunity  offers.'''^ 

Darwin  regarded  these  occasional  deviations,  these 
mutations,  as  appearing  from  time  to  time  and  in  a  gen- 
eral way  conforming  to  definite  laws  as  yet  imperfectly 
understood.  According  to  these  laws  it  could  not  hap- 
pen that  any  considerable  length  of  time  should  pass  by 
without  the  appearance  of  at  least  a  few  considerable 
variations  of  this  kind.  To  such  variations  would  be 
due  the  progress  which  the  majority  of  living  forms  ex- 
hibit in  the  course  of  the  centuries.  The  longer  the 
time  the  better  is  the  prospect  of  the  appearance  of  favor- 
able variations, 2  especially  if  these  should  only  appear 
very  seldom.*^  They  provide  us  with  ''intermittent  re- 
sults."4 

Moreover  Darwin  went  so  far  as  to  believe  in  a 
certain  periodicity.  "Nascent  species  are  more  plastic," 
that  is  to  say  produce  more  sports  and  have  therefore  a 
better  chance  of  splitting  up  into  new  species.  Darwin 
cites  Naudin  and  Herbert  as  the  authors  of  this  view, 
which  they  had  derived  from  their  comparative  studies 
of  the  forms  occurring  within  certain  groups  of  plants.^ 
Schaafhausen^  mentions  the  unequal  rate  of  the  prog- 
ress in  different  branches  of  the  genealogical  tree,  in  some 
of  them  the  changes  taking  place  very  quickly  whilst  in 
others  absolute  stagnation  seemed  to  be  the  rule  during 
long  geological  epochs.  To  produce  a  genuine  new  spe- 
cies, a  variety  must  from  time  to  time,  perhaps  at  long 

*  Loc.  a7.,  pp.  65,  66.       '^ /&f  J.,  pp.  82, 86.       ^ /^/cf.,  pp.  85, 92 

*  Ibid.,  p.  85.        ^  Ibid.,  Hist.  Sketch,  p.  xix.        ^  Ibid.,  p.  xx. 


Darzvms  Selection  Theory.  37 

intervals,  give  off  variations  in  the  same  direction.     In 
this  way  it  progresses  *'step  by  step/'^ 

Let  us  look  for  a  moment  at  Darwin's  views  on  the 
influence  of  external  conditions.  On  this  matter  again 
we  find  that  his  opinion  is  by  no  means  fixed.  Sometimes 
he  would  appear  to  think  that  it  has  played  very  little 
part  in  the  origin  of  species,  at  other  times  he  ascribes 
great  significance  to  it.  And  inasmuch  as  he  was  quite 
familiar  with  the  relation  of  individual  variation  to  the 
environment,  it  follows  that  he  was  chiefly  concerned 
here  with  single  variations.  In  a  letter  to  Hooker.  1856, 
he  says,  ''My  conclusion  is,  that  external  conditions  do 
extremely  little,  except  in  causing  mere  variability."  "How 
much  they  do  is  the  point  of  all  others  on  which  I  feel 
myself  very  weak."- 

We  are  all  familiar  in  the  pages  of  Darwin's  books 
with  the  important  role  ascribed  to  changed  conditions 
of  life.  Especially  in  the  case  of  the  transport  of  a 
plant  from  one  climate  to  another  and  the  effects  of  the 
first  years  of  cultivation  on  a  wild  species.^  Species 
therefore  with  a  wider  geographical  distribution  are 
more  likely  to  produce  new  forms. 

In  later  years  Darwin  has  again  changed  his  views 
on  this  point ;  after  reading  Hoffmann's  famous  re- 
searches he  said :  No  doubt  I  originally  attributed  too 
little  weight  to  the  direct  action  of  conditions.  Perhaps 
hundreds  of  generations  of  exposure  are  necessary.  It 
is  a  most  perplexing  subject.     (1881.)^ 

The  strongest  influence  on  Darwin  in  his  relation 
to  this  question  was  that  produced  by  a  criticism  which 
was   published   in   1869   by   Fleeming  Jen  kin   in   the 

^  Ibid.,  p.  66.  ^  Life  and  Letters,  II,  p.  87. 

^  Origin,  p.  64,  etc.  *  Life  and  Letters,  III,  p.  345. 


38  Mutability  and  Individual  Variation. 

North  British  Review.^  This  writer  tried  to  prove,  by 
calculations,  that  the  likelihood  of  single  variations  main- 
taining themselves  in  the  struggle  for  existence  or  of  ulti- 
mately being  victorious  in  it  was  very  faint.  Darwin 
allowed  himself  to  be  convinced  by  this  and  says  forth- 
with:  /  ahvays  thought  individual  differences  more  im- 
portant, but  I  was  blind,  and  thought  that  single  varia- 
tions might  be  preserved  much  oftener  than  I  now  see 
is  possible.  As  the  result  of  this  criticism  he  made  many 
alterations  in  the  subsequent  editions  of  the  Origin. 

Finally  I  shall  refer  to  the  conclusion  which  Darwin 
derived  from  his  theory  of  Pangenesis  in  its  relation  to 
these  two  forms  of  variability.^  There  are  two  abso- 
lutely different  groups  of  causes.  First,  the  relative 
number  of  the  units,  their  activity,  their  inactivity,  their 
relative  positions  and  the  calling  to  life  of  those  long  in- 
active. Such  changes  occur  without  the  units  themselves 
being  modified  by  them.  Such  changes  zvill  amply  ac- 
count for  much  fluctuating  variability,  that  is  for  that 
kind  of  variability  which  we  now  call  individual,  gradual 
or  fluctuating  variability. 

The  second  group  of  causes  includes  the  direct  effect 
of  altered  conditions  on  the  organization  of  the  indi- 
vidual, in  which  case  Darwin  supposes  the  units  them- 
selves to  be  altered.  If  the  new  units  have  then  suffi- 
ciently multiplied,  to  be  a  match  for  the  units  already  ex- 
isting they  will  lead  to  the  elaboration  of  new  structures. 

These  quotations  convince  me  that  Darwin  believed 
the  main  branches  of  his  genealogical  tree  to  have  arisen 
bv  a  modification  of  his  oremniules  and  that  he  res^arded 


^  Origin,  p.  71.    Life  and  Letters,  III,  p.  108. 

Animals  and   Plants   under  Domestication.     2d   ed.,    1875,    II, 
P-  390. 


Wallace s  Selection  Theory.  39 

fluctuating  variability  as  a  phenomenon  of  an  entirely 
different  kind.^ 

To  sum  up,  we  see  that  Darwin  always  distinguished 
between  individual  differences  and  single  variations  and 
that  he  ascribed  to  the  latter  at  least  a  very  considerable 
role  in  the  origin  of  species.  It  was  only  by  the  pressure 
of  criticism  that  he  finally  gave  up  this  view  and  gave 
the  place  of  honor  to  the  ever  present  individual  varia- 
tions. 

§  3-  WALLACE'S  SELECTION  THEORY. 

In  his  book  on  ''Darwinism"  Alfred  Russel  Wal- 
lace has  collected  in  an  excellent  and  convincing  manner 
a  valuable  mass  of  evidence  for  the  theory  of  descent.^ 
Few  authors  except  Darwin  have  taken  such  a  prom- 
inent part  in  fighting  for  this  theory,  as  he.  His  book 
''Darwinism"  consists  essentially  of  two  parts.  In  the 
first  sections  Wallace  deals  with  variability  and  selec- 
tion, in  the  second  he  describes  the  wonderful  adapta- 
tions of  animals  and  plants  to  their  environment  and 
seeks  to  explain  them  on  the  basis  of  Darwin's  theory 
by  bringing  out  as  forcibly  as  possible  the  agreement 
between  the  demands  of  the  theory  and  the  facts  them- 
selves. This  latter  half  is  undoubtedly  the  most  interest- 
ing of  the  whole  work.  But  I  shall  only  discuss  his 
theory  of  selection  in  this  book. 

Wallace's  selection  theory  differs  from  that  of 
Darwin  in  one  essential  point.  Wallace  regards  the 
ever  present  individual  variation  as  the  material  from 
which  natural  selection  forms  new  species.     It  is  his  main 

^  See  also  my  Intraccllularc  Pangenesis,  pp.  73-74,  210,  etc. 

^  A.  R.  Wallace,  Darzvinism,  an  Exposition  of  the  Theory  of 
Natural  Selection  zvith  Some  of  its  Applications.  London,  1889, 
2d.  ed. 


40  Mutability  and  Individual  Variation. 

object  to  show  that  animals  and  plants  do  perpetually 
vary  in  the  manner  and  to  the  amount  requisite.^  Single 
variations  he  regards  as  absokitely  without  significance; 
they  have  played  no  part  (he  says),  or  at  most  hardly 
any,  in  the  origin  of  species.^ 

Our  author  holds  himself  to  be  at  one  with  Darwin 
in  essentials  and  only  to  have  rendered  his  selection 
theory  sharper  and  more  precise.  The  hosts  of  doubts 
which,  as  we  saw  in  the  preceding  section,  were  always 
so  carefully  brought  forward  and  discussed  by  Darwin, 
disappear.  The  theory  has  become  a  compact,  clear  and 
surprisingly  simple  one.  Wallace  takes  just  as  careful 
account  of  the  systematic  and  biological  facts  as  Darwin 
did  in  his  cautious  way,  but  Wallace^s  theory  is  much 
more  convenient  and  attractive  than  Darwin's. 

This  very  clearness  in  the  mode  of  presentation  makes 
it  easy  for  the  critic  to  discover  the  weak  spot.  In  fact 
the  author  himself  almost  lays  his  finger  on  it.  At  the 
end  of  the  first  section  he  gives  a  summary  of  his  collec- 
tion of  facts  and  the  method  of  his  proof ;  and  one  has 
only  to  follow  carefully  to  discover  the  weak  point  in 
his  argument.'^ 

It  will  be  useful  to  recapitulate  as  briefly  as  may  be 
this  argument. 

Wallace's  theory  of  natural  selection  rests  on  two 
series  of  facts.  The  first  is  the  rapid  multiplication  and 
the  resulting  premature  death  of  innumerable  individuals. 
The  second  is  variability  and  the  survival  of  the  fittest. 
Against  this  part  of  his  argument  I  have  no  objection  to 
raise.     He  then  goes  on  to  consider  another  im.portant 

^Darwinism,  2d.  ed.,  p.  13. 

'"My  whole  work  tends  forcibly  to  illustrate  the  overwhelming 
importance  of  natural  selection."     Wallace,  loc.  cit.,  pp.  vii-viii. 

^Darwinism,  pp.  12,  13. 


Wallace's  Selection  Theory.  41 

point.  This  point  concerns  the  principle  of  the  inherit- 
ance of  variations  and  the  artificial  improvement  of 
races  by  selection.  In  many  cases  cultivated  forms  have 
become  so  different  from  their  wild  ancestors  by  this 
means,  that  they  can  scarcely  be  recognized  as  their 
descendants.  But  the  word  races  has  evidently  a  double 
signification.  It  means  not  only  the  races  improved  by 
selection,  but  also  the  constant  subspecies  of  unknown 
origin  which  already  exist.  ^  Without  doubt  many  culti- 
vated forms  diverge  to  a  certain  extent  from  the  species 
to  which  they  are  considered  to  belong  by  systematists. 
But  these  forms  are  subspecies  and  their  common  origin 
from  a  single  species  is  just  as  good  a  hypothesis  as  that 
of  the  common  origin  of  the  species  of  a  genus.  Culti- 
vated subspecies  are  in  well-known  cases  older  than  cul- 
tivation itself;  as  Wallace  himself  for  example  shows 
in  the  case  of  the  races  of  the  dog.^  How  they  have 
arisen  we  do  not  know,  not  even  in  the  case  of  those  that 
have  probably  arisen  in  a  state  of  domestication. 

On  this  slender  foundation  Wallace  now  proceeds 
to  build  further,  and  says,  p.  12:  ''It  is  therefore  proved 
that  if  any  particular  kind  of  variation  is  preserved  and 
bred  from,  the  variation  itself  goes  on  increasing  in 
amount  to  an  enormous  extent;  and  the  hearing  of  this 
on  the  question  of  the  origin  of  species  is  most  im- 
portant/' 

But  this  thesis  is  by  no  means  proved ;  on  the  con- 
trary its  truth  is  only  assumed  for  the  sake  of  the  argu- 
ment both  by  Darwin  and  Wallace,  and  by  the  mass 
of  their  followers. 

Wallace  evades  this  point  in  his  book;    he  neither 

^  As  for  instance  the  races  of  mankind. 
^  Loc.  cit.,  p.  88. 


42  Mutability  and  Individual  Variation. 

subjects  it  to  a  stringent  criticism  nor  does  he  devote 
a  separate  section  to  it.  Furthermore  in  the  treatment 
of  single  instances  this  thesis  is  taken  for  granted  with- 
out further  proof.  One  sees  this  most  clearly  in  the 
discussion  of  the  apple  :^  It  is  known,  he  says,  that  all  our 
kinds  of  apples  spring  from  the  wild  Pyrus  Mains  and 
that  from  this  over  a  thousand  different  forms  have  been 
developed.  This  gives  one  the  impression  that  cultiva- 
tion produced  these  numerous  forms.  But  as  a  matter 
of  fact  the  apple  in  the  wild  condition  is  a  polymorphous 
species  rich  in  subspecies  and  the  w^ell  differentiated  types 
which  are  now  cultivated  already  exist  among  the  wild 
forms.  The  transformation  of  the  wild  crab  apples  into 
juicy  and  finely  flavored  fruits  is  all  that  has  been  brought 
about  by  cultivation. 

It  is  an  absolutely  unproved  assumption  that  individ- 
ual variation  extends  its  range  by  selection  and  increases 
"to  an  enormous  extent^  This  is  the  weak  point  in 
Wallace's  selection  theory. 

I  admit  that  with  this  assumption  it  would  be  very 
easy  and  simple  to  account  for  the  phenomena  of  adap- 
tation, and  that  this  forms  a  very  strong  argument  for 
it.  And  if  it  were  only  a  matter  of  this  explanation  little 
purpose  would  be  served  by  raising  objections  to  it. 

But  it  is,  as  a  matter  of  fact,  fallacious.  Selection 
certainly  leads  to  enormous  practical  results,  but  that  is 
a  very  different  thing  from  enormous  biological  changes. 
The  fact  that  a  man  can  increase  the  yield  per  acre  by 
one-half,  has  no  significance  from  the  point  of  view  of 
the  origin  of  species.  In  the  third  chapter  I  shall  seek 
to  prove  this  by  the  help  of  facts. 

it  is  not  necessary  to  follow  Wallace's  argument 

*  Loc.  cit.,  p.  87. 


The  Various  Forms  of  Variability.  43 

further.  If  his  assumption  is  once  granted  everything 
else  follows.  On  page  13  he  again  sums  up  his  position. 
He  is  concerned  there  to  show  that  variations  of  every 
kind  can  be  increased  and  accumulated  by  selection  not 
only  in  the  cultivated  but  in  the  wild  condition.  I  fully 
admit  that  Wallace  has  effected  this  proof  in  a  masterly 
and  convincing  manner.  But  we  also  require  proof  that 
this  increase  and  accumulation  takes  place  ''to  the  amount 
requisite''  for  the  origin  of  new  species  and  subspecies; 
and  this  proof  Wallace  neither  brings  forward  nor 
seeks.  Instead  of  it,  his  book  is  full  of  instances  of  the 
compound  nature  of  cultivated  and  of  wild  species  and 
of  their  so-called  elementary  or  subspecies  ;^  but  how 
these  have  arisen  we  are  not  told.  He  has  equally  little 
success  in  proving  that  races  which  have  arisen  by  selec- 
tion remain  constant  without  further  selection. 

Finally,  we  see  that  Wallace  in  his  selection  theory 
starts  from  individual  or  ordinary  variability  and  allows 
no  share  in  the  process  to  single  variations.  He  shows 
that  the  hypothesis  thus  simplified  effectively  coordinates 
systematic  and  biological  facts,  but  he  fails  in  proving 
that  as  a  matter  of  fact  specific  characters  can  really 
arise  by  the  selection  of  individual  differences. 

§  4.  THE  VARIOUS  FORMS  OF  VARIABILITY. 

Nothing  is  more  variable  than  the  meaning  of  the 
word  variability.  Many  authors  use  this  word  in  so 
comprehensive  a  sense  that  one  cannot  understand  what 
they  mean.      (Fig.  8.) 

It  is  therefore  important  to  distinguish  as  clearly  as 
possible  between  the  various  phenomena  included  under 

See  for  example  pp.  77-78,  85-86,  etc. 


44 


Mutability  and  Individual  Variation. 


this  term.     For  they  stand  in  absokitely  different  relation 
to  our  thesis. 

The    following  groups    of   phenomena    usually    fall 
within  the  meaning  of  the  term  variability: 


Fig.  8.    Hedera  Helix  var,  arhorea} 

1.  Systematic  polymorphism  and  its  supposed  causes. 

2.  Polymorphism  caused  by  crossing. 

^  The  best  known  example  is  afforded  by  Hedera  Helix  arhorca 
whicli  is  offered  by  many  nurseiymen  as  var.  arborca.  It  is  not  a 
variety,  but  consists  simply  of  the  erect  flowering  shoots  cut  off  the 
ordinary  ivy,  stuck  in  the  ground,  and  grown  as  trees.  In  April  i88S 
I  made  some  such  cuttings,  and  have  cultivated  the  best  one  till  the 
present  time.  It  forms  a  richly  branched  bush  over  a  meter  higli 
(Fig.  8).  As  is  shown  in  the  figure  at  a,  b,  c,  creeping  branches 
arise  from  time  to  time.  In  1893  I  sowed  the  berries  of  an  older 
plant  of  this  kind,  in  this  case  an  ivy  bush  of  about  two  meters,  and 
obtained  over  a  thousand  seedlings.  These  still  grow  in  our  garden 
and  have  made, up  till  now,  exclusively  creeping  stems  and  branches. 
The  Arborea-iorm  is  evidently  not  inherited.  Similar  phenomena 
occur  in  many  other  genera,  for  example  in  the  creeping  species  of 
figs  in  South  Europe ;  but  they  have  not  been  sufficiently  investigated. 


The  Various  Forms  of  Variability.  45 

3.  The  differences,  in  individuals  and  organs,  which 
follow  Ouetelet's  law. 

4.  The  so-called  spontaneous  variations. 

The  special  problem  which  the  mutation  theory  seeks 
to  explain  is  the  manifold  diversity  of  specific  forms; 
spontaneous  variations  are  the  facts  on  which  this  ex- 
planation is  based.  The  truth  of  this  explanation  will  then 
be  tested  by  its  application  to  hybrids;  and,  if  possible, 
proved.  Individual  variability  however  will  be  shown 
to  be  of  only  secondary  importance. 

It  will  be  convenient  to  deal  with  these  groups  one 
by  one. 

1.  Systematic  Polyinorphism  and  its  Supposed  Causes. 

Linnean  species  are  aggregate  species.  They  include 
sometimes  a  small  but  often  a  large  series  of  forms  which 
are  as  sharply  and  completely  distinguished  from  one 
another  as  are  the  best  species.  These  lower-rank  forms 
are  usually  called  varieties  or  subspecies;  varieties,  if 
they  are  characterized  by  a  single  striking  character,  but 
subspecies  if  they  are  distinguishable  by  the  sum  of  their 
characters,  by  their  so-called  habit.  But  on  this  point 
there  is  a  great  diversity  of  opinion.  Some  authors  re- 
gard all  these  special  forms  as  elementary  species  and 
consequently  give  them  double  names,  thereby  breaking 
up  the  Linnean  species.  It  is  well  known  that  in  this 
way  Draha  verna^  and  Viola  tricolor-  and  many  other 
old  species  have  been  broken  up  (in  the  case  of  Draha 
verna  into  200)  smaller  groups  of  perfectly  distinct  and 
usually  local  elementary  species.  By  experiment  and 
culture  these  forms  prove  constant,  they  do  not  change 
into  one  another,  nor  do  they  reproduce  the  typical  or 
general  form  of  the  species.     The  majority  of  varieties 

*  See  Fig.  3  on  page  22.  '  See  Fig.  4  on  page  2;^. 


46  Mutability  and  Individual  Variation. 

are  just  as  constant  as  these.  Whether  we  give  them 
binary  and  ternary  names  is  not  of  much  consequence. 
It  has  always  been  assumed  both  before  and  after  Dar- 
win's time,  that  they  have  a  common  origin,  biit  in 
remarkably  few  cases  is  there  historical  evidence  that 
this  is  so.  When  and  how  Datura  Stramonium  inermis, 
Rohinia  Pseud-Acacia  inermis,  Lychnis  diurna  glaber- 
rima,  and  the  wdiole  series  of  glabrous  thornless,  white- 
flowered,  laciniate  forms,  and  so  forth,  have  arisen  we 
do  not  know.  They  exist  and  claim  recognition  equally 
with  the  best  species.  There  are  a  few  exceptions,  for 
example  Chclidonium  laciniatwn  Mill.  (Fig.  Z7  in  V, 
§  25),  Fragaria  alpina  Gaillon  (Fig.  7,  p.  30),  etc.,  whose 
source  is  known. 

In  practical  horticulture  matters  are  just  as  bad.  End- 
less varieties  are  known  but  only  in  rare  cases  is  there 
any  historical  information  as  to  their  origin.^ 

This  section  of  the  subject  of  variability  therefore  is 
a  purely  comparative  one,  its  laws  are  morphological, 
and  only  rarely  does  it  lend  itself  to  historical  or  experi- 
mental study. 

2.  Polymorphism  induced  by  hybridization  is  due  to 
new  combinations  of  the  heritable  characters  of  the  forms 
crossed.  Two  groups  of  phenomena  must  be  distinguished 
here :  scientific  experiment  and  horticultural  and  agricul- 
tural crosses.  The  scientific  investigator  chooses,  if  he  can, 
the  least  'Variable"  species  whilst  the  gardener  prefers  to 
cross  types  of  which  at  least  one  is  very 'Variable."  For 
this  variability  can  be  inherited  by  the  hybrid  and  increases 
the  likelihood  of  getting  new  forms ;  and  this  is  of  coarse 


*  (Note  of  1908.)  A  most  interesting  and  complete  list  of  these 
instances  has  since  been  given  by  Kokschinsky.  See  Flora,  1901,  Bd. 
59,  pp.  240-363. 


The  Various  Forms  of  Variability 


47 


what  is  wanted.  New  elementary  characters  arise  in 
hybridization  experiments  solely  through  this  kind  of 
variability,  and  not  as  the 
result  of  the  crossing  it- 
self; as  for  example  Al- 
fred Bleu,  the  distinguished 
raiser  of  Caladiums,  has  as- 
sured me  to  be  the  case  with 
his  cultures. 

3.  Variability  in  the  re- 
stricted sense  or  individual 
variability,  is  the  name  given 
to  those  dissimilarities  of  in- 
dividuals and  organs,  which 
can  be  described  in  terms  of 
Ouetelet's  laws.^ 

These  laws,  with  which 
Darwin  was  not  familiar, 
and  which  were  only  imper- 
fectly dealt  with  by  Wal- 
lace^ have  since  that  time 
been  the  subject  of  close  investigation ;  with  the  result 
that  it  has  become  increasingly  evident  that  these  varia- 

^  See  Figs.  9-13;  also  Fig.  22  (curve  of  40.000  beets)  in  chapter 
3,  §  II,  where  also  the  theoretical  curve  is  shown. 

^  Case  containing-  beans  to  demonstrate  their  variability  in  length. 
The  glass  case  is  divided  by  strips  of  glass  into  nine  equal  partitions. 
About  450  beans  ( redspotted  seeds  of  Phascolus  vulgaris)  were 
picked  from  a  bought  sample  and  the  individuals  measured.  Their 
length  varied  between  8-16  millimeters,  and  in  the  following  pro- 
portions : 

Partitions   .   .  .  .    i         2         3         4         5         6         7         S        9 

mm. 8        9       10       II       12       13       14       15       16 

number i         2       23     108     167     106       2>}>         7     .    ^ 

The  beans  were  then  placed  in  the  subdivisions  of  the  jar,  in  such 
a  way  that  each  compartment  only  contained  beans  of  the  same 
length  (measured  in  whole  millimeters)  and  in  the  order  shown 
above.     Without  further  treatment  the  beans  show  a  grouping  ac- 


Fig.  9.  Glass  Jar  with  Beans.^ 


48 


Mutability  and  Individual  Variation. 


tions  are  of  an  entirely  different  nature  from  the  rest 
of  the  phenomena  included  under  the  name  of  variability. 
They  have  this  in  common  that  they  are  always  present 
and  can  be  observed  every  year  and  in  every  group  of 


2         23       /ns       167      ;o6      33 

'  Fig.  10.  Curve  of  Beans/ 

individuals  provided  it  is  not  too  small.  They  are  always 
grouped  round  a  mean,  and  the  numbers  of  the  deviations 

cording  to  Quetelet's  law.  For  a  more  exact  demonstration  a  cor- 
rection would  be  necessary,  since  obviously  the  larger  beans  fill  up 
their  compartment  more  than  a  similar  number  of  small  ones. 

^  Curve  of  the  red-spotted  beans.  The  curve  is  plotted  from  the 
observations  reproduced  in  Fig.  9.  It  corresponds  to  the  theoretical 
form  (a-f^)"  sufficiently  exactly,  as  is  evident  by  mere  inspection. 
The  length  of  the  ordinates  is  proportional  and  almost  equal  to  the 
corrected  height  of  the  groups  of  beans  belonging  to  each  compart- 
ment of  the  glass  case.  The  number  of  beans  found  in  each  com- 
partment is  found  at  the  foot  of  the  corresponding  ordinate.  A  bean 
from  each  group  is  drawn  as  a  sample  to  show  the  extent  of  fluc- 
tuating variability  in  length.  The  beans  are  seen  to  be  very  variable 
in  form  and  coloring  also. 


The  Various  Forms  of  Variability. 


49 


from  this  mean  are  inversely  proportional  to  their  mag- 
nitude. The  variation  may  be  exhibited  in  size  or  number 
and  the  results  of  observation  can  be  treated  by  mathe- 
matical signs  and  formulae. 

Galton,  Weldon,  Bateson^  Ludwig,  Duncker, 
and  many  other  investigators  have  raised  this  line  of 
inquiry  to  a  special  branch  of  science.  But,  unfortunately, 
a  recognized  term  for  the  phenomena  with  which  they 
deal  does  not  exist.  It  has  been  called  fluctuating,  grad- 
ual, continuous,  reversible,  limited,  statistical  and  indi- 
vidual variability.  The  latter  seems  to  be  the  most  widely 
distributed  in  zoological  and  anthropological  literature, 


Fig.  II.  The  Ogive-form  of  the  curve  of  individual  variation, 
made  of  the  leaves  of  Pvumis  Lauro-Cerasus.^ 


while  tlie  name  fluctuating,  which  was  often  used  by 
Darwin^  seems  to  be  the  best.^  On  the  botanical  side 
individual  is  opposed  to  partial  variability,  the   former 

^  Individual  variability  can  be  very  simply  demonstrated  by  past- 
ing the  leaves  of  a  tree  in  a  row  side  by  side.  They  are  arranged 
according  to  their  size  and  are  placed  at  equal  distances  along  a 
horizontal  base  line  in  such  a  way  that  their  midribs  are  parallel ; 
then  their  tips  are  joined  by  a  line.  In  the  above  figure  this  line  is 
placed  at  a  little  distance  from  the  tips  of  the  leaves  for  the  sake  of 
clearness.  This  line  (the  Ogive  of  Galton,  who  has  made  most  use 
of  it)  at  first  mounts  quickly,  then  in  the  middle  only  slightly  and 
at  the  end  rapidly  ascends  again,  following  Qi'Etelet's  law.  The 
points  Q,  M,  Q  divide  it  into  4  quarters   (Q  =  Quartile). 

^  See  KoLLMANN  in  Correspondenz-Blatt  d.  d.  Gesellsch.  f.  An- 
thropologic, Bd.  31.  No.  I,  Jan.  1900. 


50 


Miitahility  and  Individual  Variation. 


meaning  the  differences  between  individuals,  and  the 
latter  the  equally  frequent  differences  between  the  organs 
of  a  single  individual. 

The  necessity  of  distinguishing  between  variability 
in  space  and  time  has  been  often  insisted  upon;^  I  mean 
between  (a)  the  diversity  in  a  group  of  forms  existing 
at  the  same  time,  and  (b)  the  differences  existing  between 


K%  tZJ     13     13Z     Tt      ns    IS      ISj     10     ItiJ     17     17.5     18    I3.S     (9 


Fig.  12.  Amount  of  Sugar  in  Beets,  at  Naarden." 

On  January  24,  1896. 

— On  January  25,  1896. 

On  January  28,  1896. 

parents  and  their  children,  and  more  distant  descendants. 
Ploetz  has  proposed  that  contemporary  varying   indi- 

^  W.  Waagen,  Die  Formcn  des  Ammonites  suhradiatns  in  Be- 
necke's  Geognostisch-Palaontologische  Beitriige,  1876,  Bd.  II,  p.  1S6. 

^  The  three  curves  exhibit  the  sugar  contents  of  beets  from  one 
large  sample  taken  from  three  successive  determinations  on  January 
24th,  25th  and  28th,  1896,  by  exactly  the  same  method.  The  num- 
bers in  each  lot  were  6848,  6781  and  6191,  amounting  almost  to 
20,000  polarizations.  The  sugar  contents  varied  from  about  12  to 
19  per  cent.  These  figures  I  owe  to  the  generosity  of  Messrs.  Kuhn 
&  Co.,  the  owners  of  the  factories  at  Naarden. — In  spite  of  the  con- 
siderable number  of  values  taken  the  curves  do  not  exactly  coincide. 
The  third  curve  taken  3  days  later  has  its  apex  shifted  a  little  to 
the  right.  The  differences  between  the  2  others  are  obviously  to 
be  attributed  to  unavoidable  chance  circumstances.  In  the  compari- 
son of  empirical  curves  with  theoretical  ones,  a  closer  agreement 
than  that  between  2  curves  from  2  samples  of  the  same  kind  must 
obviously  not  be  expected.  For  theoretical  purposes  therefore  one 
should,  where  possible,  compare  two  or  more  curves  of  the  same 
phenomenon. 


The  Various  Forms  of  Variability.  51 

viduals  should  be  called  Convariants,  successive  ones  De- 
variants;^  and  individuals  departing  widely  from  the 
mean  are  often  called  variants. 

Individual  variability  is  exhibited  by  size,  weight  and 
number;  Ludwig^s  countings  on  flowers  conform  to  Que- 
telet's  laws  as  accurately  as  the  anthropological  meas- 
urements of  that  great  writer  himself.  Variations  in 
size  and  weight  should  be  called  quantitative,  and  Bate- 
son  has  proposed  for  variation  in  numbers  the  name 
discontinuous  or  meristic.^ 

Darwin  asserted  over  and  over  again  that  this  form 
of  variability  ^'perpetually  occurs."  It  could  therefore 
be  described  as  perpetual  or  incessant,  and  tliis  idea 
seems  to  me  to  be  best  expressed  by  the  word  continu- 
ous."' 

Individual  variability,  when  tested  by  sowing,  reverts 
to  its  original  mean,  the  forms  of  its  variants  are  con- 
nected together,  are  coherent  and  not  discontinuous.  It 
is  centripetal  inasmuch  as  the  variations  are  grouped  most 
densely  round  a  mean.  Finally — and  this  is  very  im- 
portant— it  is  linear;  because  the  deviations  occur  in 
only  two  directions — less  or  more.  This  fact  has  given 
rise  to  the  expressions  plus-variations  and  minus-varia- 
tions. 

It  is  to  the  selection  of  the  material  afforded  by  in- 
dividual variability  that  the  origin  of  many  improved 

*  Alfred  Ploetz,  Die  Tilchtigkeit  iinserer  Rasse  iind  dcr  Schuts 
der  Schzvachen,  I,  1895,  P-  3i- 

^Materials  for  the  Study  of  Variation. 

^  I  have  used  the  terms  continuous  and  discontinuous  in  this 
sense  in  my  essay  Ueher  halbe  Galton-Curven  als  Zcichen  discon- 
tinuirlichcr  Variation.  (Berichte  d.  d.  Bot.  Gcs.,  1894,  Bd.  XII, 
Heft  7).  Bateson  uses  the  word  in  a  sHghtly  different  sense  inas- 
rnuch  as  he  employs  the  term  continuous  solely  for  quantitative,  and 
discontinuous  for  meristic  variations  {Materials  for  the  Study  of 
Variation,  1894). 


52 


Mutability  and  Individual  Variation. 


races  is  due.  But  we  must  not  forget,  what  we  have 
ah'eady  mentioned,^  that  the  word  "race"  is  used  here  in 
a  different  sense  from  that  in  which  it  is  used  in  anthro- 
pology. The  principal  difference  between  the  so-called  im- 


/ 

^ 

h 

. 

/ 
/ 
/^ 

f  1 
I'f 

t  1 

1 

r^\    !   \^^ 

J 

\ 

'■•J                     ^ 

2lMm22      23       Zii 


26      27        2a      29 


it       32       33      3<> 


Fig.  13.  Exhibition  of  Variability  by  the  Fan  Type  of  Plotting.^ 

proved  races  on  tlie  one  hand,  and  varieties,  subspecies, 
elementary  species,  incipient  species  and  so  forth,  on  the 
other,  will  form  the  subject  of  our  third  chapter. 

^  See  page  41. 

^  VariabiHty  can  be  exhibited  by  other  means  than  l)y  Quetelet's 
curve  (Fig.  10)  or  Galton's  Ogive  (Fig.  11).  If  it  is  a  question 
of  comparing  successive  generations  with  one  another  the  "fan" 
type  of  presentation  (Fig.  13)  is  to  be  recommended.  The  point 
from  which  the  rays  emanate  gives  the  character  of  the  mother 
plant.  The  length  of  the  base  of  each  triangle  on  the  upper  hori- 
zontal line  gi\'es  the  length  of  the  ordinates  in  an  ordinary  curve,  as 
they  are  drawn  above  in  the  diagram.  This  breadth  gives  at  a  glance 
the  frequency  of  individuals  for  any  one  scale  character.  The  data 
for  this  figure  consist  of  measurements  of  the  length  of  the  ripe 
fruits  of  Oenothera  Lamarekiana  taken  in  the  year  1891  (99  fruits 
measured  in  whole  millimeters).  The  lengths  were  distributed  in 
the  following  way  over  the  fruits: 

mm.  21     22    23    24    25     26    27    28    29    30    31     32    2)2)    34 
I       I       7      8     14     15     12     13       5      7      5      4      4      3 
The  crooked  line  follows  Quetelet's  law   (a-J-Z?)". 


The  Various  Forms  of  Variability.  53 

4.  Spontaneous  changes.  We  have  long  been  familiar 
in  practical  horticulture  with  the  phenomenon  of  the  sud- 
den and  unexpected  appearance  of  varieties  from  time 
to  time.  Darwin  calls  these  sudden  transitions  single 
variations. 

The  finest  examples  are  the  so-called  bud  variations. 
The  new  form  arises  as  a  bud  or  twig  on  an  individual 
of  the  old  form  and  often  remains  a  long  time  united 
with  it.  In  a  case  like  this  there  can  be  no  doubt  as  to  the 
mutual  genetic  relationship,  and  the  fact  that  the  transi- 
tion is  discontinuous  is  at  once  evident.  But  even  in  this 
sphere  there  is  great  uncertainty  because  bud  variations 
are  often  born  by  hybrids  and  the  hybrid  nature  of  an 
individual  is  sometimes  even  betrayed  only  by  such  varia- 
tions. Moreover  bud  variations  are  very  common  on 
varieties  with  incompletely  fixed  (mixed)  characters,  as 
in  many  forms  with  striped  flowers  (Antirrhinum,  Del- 
phinium, Aquilegia,  Dahlia,  Fig.  14,  etc.) 

5.  On  the  Magnitude  of  Mutations.  We  often  hear 
of  spontaneous  changes  described  as  sports  or  as  sport- 
like variations.  This  term  is  not  a  happy  one.  Natura 
non  facit  saltus,  said  Linnaeus.  But  we  are  not  told 
what  we  are  to  regard  as  a  jump.  There  is  much  more 
point  in  describing  the  individual  transitions  as  jerks 
and  to  speak  of  jerky  variability.^  The  jerks  may  only 
induce  quite  small  changes,  but  each  jerk  represents  a 
distinct  unit. 

Galton  has  illustrated  the  difference  between  jerk- 
ing and  ordinary  variability  in  a  very  beautiful  way. 
Imagine  a  polyhedron  which  can  roll  on  a  flat  surface.^ 
Every  time  that  it  comes  to  rest  on  a  fresh  side  it  takes 

^  "Variation  par  secousses"  of  some  French  writers. 
F.  Galton,  Hereditary  Genius,  1869,  p.  369. 


54 


Mutability  and  Individual   Variation. 


Fig.  14.  Striped  Dahlias  (Dahlia  variabilis  striata  nana), 
grown  from  seed.  The  central  flower  of  the  plant  in 
the  middle  had  yellowish  red  stripes  on  a  pale  red 
ground ;  the  left  flower  on  the  same  plant  had  one-half 
(shaded  darker  in  the  figure)  entirely  red,  the  other 
reddish  yellow  and  pale  red  stripes.  The  two  separate 
flowers  figured  below  were  of  other  color  varieties ;  in 
the  right  one  red  stripes  were  on  a  white  ground,  in  the 
left  dark  violet  stripes  on  a  pale  violet  ground.  The 
first  plant  had  branches,  in  1898,  whose  flowers  were  en- 
tirely red,  afl'ording  an  example  of  so-called  bud-varia- 
tion. 


The  Various  Forms  of  Variability.  55 

up  a  new  position  of  equilibrium.  Little  shocks  make 
it  totter ;  it  oscillates  round  its  position  of  equilibrium 
and  finally  returns  to  it.  A  slightly  stronger  push  how- 
ever can  make  it  go  so  far  that  it  comes  to  lie  on  a  new 
side.  The  oscillations  round  a  position  of  equilibrium 
are  the  fluctuations,  the  transitions  from  one  position 
of  equilibrium  to  another  correspond  to  the  mutations. 
The  track  left  behind  by  the  rolling  polyhedron  can  be 
regarded  as  the  line  of  descent  of  the  species ;  each  sub- 
division of  this  track,  corresponding  to  a  side  of  the 
polyhedron,  representing  a  particular  elementary  species ; 
each  transitional  movement  to  a  new  position  a  muta- 
tion. 

The  more  numerous  one  imagines  the  sides  of  such 
a  polyhedron  to  be,  the  smaller,  of  course,  are  the  muta- 
tions. But  this  illustration  gives  no  insight  into  the 
causes  which  effect  the  changes  in  position. 

The  observation  of  many  single  variations  has  intro- 
duced the  view  that  mutations  must  always  be  consider- 
able changes  and  especially  that  they  should  be  greater 
than  variations.  But  this  is  by  no  means  the  case,  and 
it  appears  that  many  mutations  are  smaller  than  the 
differences  between  extreme  variants.  This  is  imme- 
diately clear  if  one  compares  e.  g.  Draha  vcrna  or  TypJia 
angitstifoUa  and  latifoUa.  The  single  species  of  Draha 
verna  (discriminated  by  Jordan,  De  Bary,  Rosen  and 
others),  which  have  been  shown  by  repeated  sowing  to 
be  constant,  differ  less  from  each  other  than  extreme 
variations  in  the  same  characters  (form  and  size  of  the 
leaves,  petals,  pods,  etc. )  usually  do  in  other  plants ;  as 
can  be  seen  best  by  comparing  them  with  the  partial 
variations  of  the  leaves  of  our  trees,  that  is,  with  the 
differences  between  the  various  leaves  of  one  and  the 


56  Mutability  and  Individual  Variation. 

same  tree.  And  Davenport  and  Blankinship  have 
recently  shown  in  a  valuable  paper  that  in  the  case  of 
Typha  latifolia  and  augustifolia  the  curves  describing 
their  various  characters  overlap.  A  small  leaf  of  latifolia 
can  be  smaller  than  the  broadest  leaf  of  augustifolia  and 
so  forth.  Tlie  curves  overstep  the  limits  between  two 
species;  they  are  transgressive  and  the  species  become 
''inter grading  groups:'^ 

The  differences  between  the  single  species  of  Draha 
vcrna  (Fig.  3)  afford  one  of  the  best  examples  for 
making  clear,  in  a  general  way,  the  nature  and  size  of 
mutations. 

§  5.  THE  ELEMENTS  OF  THE  SPECIES. 

Ever  since  Darwin's  theory  of  descent  obtained  gen- 
eral recognition,  the  need  of  an  experimental  study  of 
the  origin  of  species  has  always  been  strongly  felt.  This 
demand  was  always  kept  in  the  forefront  by  the  few 
opponents  of  this  theory,  who  objected  that,  so  long  as  it 
was  not  possible  to  produce  new  species,  or  at  least  ob- 
serve their  origin  directly,  the  foundation  on  which  the 
theory  rested  was  one  of  unproved  h3^pothesis. 

In  the  discussion  of  this  objection  two  entirely  differ- 
ent things  are  usually  confounded.  The  origin  of  species 
is  not  the  same  thing  as  the  origin  of  specific  characters. 
The  former  is  a  historical  occurrence ;  the  latter  is  a 
physiological  one.  How,  when  and  where  species  exist- 
ing at  the  present  moment  arose  is  a  subject  for  historical 
investigation,  and  we  can  only  discover  anything  definite 
about  it  in  those  rare  cases  in  which  records  have  been 
kept  by  contemporary  eye-witnesses.     The  problem  of 

^  C.  B.  Daxtnport  and  J.  W.  Blankinship,  A  Precise  Criterion 
of  Species;  Science,  N.  S.,  Vol.  H,  No.  177,  p.  685,  1808. 


The  Elements  of  the  Species.  57 

accurately  tracing  the  formation  of  a  given  species  is 
certainly  a  most  attractive  one ;  but  its  solution  falls 
within  the  province  of  comparative  biology. 

The  origin  of  specific  characters  is  a  matter  for 
physiological  investigation,  and  is  of  the  very  highest 
importance.  AVe  hardly  know  what  specific  characters 
are.  We  know,  it  is  true,  that  elementary  species  and 
form.s  closely  allied  to  them,  are  distinguished  from  one 
another  not  by  a  single  feature  but  by  all  their  organs 
and  peculiarities.^  The  difi^erences  between  two  closely 
allied  forms  often  demand  a  long  and  extensive  diagnosis. 
Nevertheless  this  diagnosis  must  be  regarded  as  the  ex- 
pression of  a  single  character,  a  single  unit,  which  arose 
as  such  and  as  such  can  be  lost;  the  individual  factors 
of  which  cannot  be  manifested  separately.  Theoretically 
such  a  group  of  characters  must  be  regarded  as  a  unit, 
as  a  single  character.^  It  forms  a  single  side  of  Galton's 
polyhedron  (p.  53).  Darwin  called  such  characters 
the  elements  of  the  species  and  consequently  we  may 
call  each  of  the  forms  distinguished  by  such  an  element, 
an  elementary  species. 

How  these  elements  of  the  species  arise  must  sooner 
or  later  become  the  subject  of  experimental  investigation. 
If  we  once  succeed  in  solving  this  question  we  shall  ob- 
tain not  only  a  much  surer  foundation  for  the  theory  of 
descent  but  the  prospect  of  the  utilization  of  this  discov- 
ery for  the  benefit  of  mankind.  The  only  means  by 
which  the  breeder  can  get  new  forms  is  by  hybridization, 
and  all  that  he  can  do  by  selection  is  to  intensify  the 
produce   and   yield   of   characters   already   present ;   but 

^  This  fact  forms  a  hitherto  little  noticed  support  for  the  theory 
of  homotypic  cell-divisions  as  advanced  by  Hertwig  and  others  and 
by  myself  in  my  Iniracellulare  Pangenesis  (See  e.g.  p.  115). 

^  Tniracellulare  Pangenesis,  p.  i6. 


SS  Mutability  and  Individual  Variation. 

so  far  it  is  not  within  his  power  to  call  into  existence  new 
characters.  We  all  know  that  it  is  said  to  be  impossible 
to  produce  a  blue  Dahlia,  a  bright  yellow  Hyacinth  and 
so  forth.  To  give  our  large  flowered  Canna  white  flow- 
ers we  must  wait  for  the  discovery  of  a  new  white  flow- 
ered wild  species  and  then  cross  it  with  it  (Crozy)  ;  in  the 
same  way  that  our  Gladioli  have  been  made  hardy  and 
the  flowers  of  our  Begonias  large  by  crossing  them  with 
newly  discovered  species  which  possess  the  character  in 
question.  As  soon  as  we  arrive  at  an  experimental  phys- 
iology of  the  origin  of  species,  we  expect  to  obtain  con- 
trol over  much  that  at  present  seems  beyond  our  reach. 

But  let  us  return  to  the  facts.  Whilst  w^e  may  hope 
that  the  origin  of  new  elementary  species  will  one  day 
become  the  subject  of  direct  investigation,  we  must  be 
perfectly  clear  as  to  the  essential  difference  between  these 
and  the  so-called  Linnean  species  which  are  (usually) 
groups  of  elementary  species.  An  elementary  species 
can  be  identified  in  anv  e^iven  case  bv  the  test  of  culti- 
vation ;  how  many  such  forms  should  be  united  to  one 
Linnean  species  is  a  matter  for  so-called  taxonomic  in- 
stinct, just  as  is  the  settlement  of  the  limits  of  genera 
and  families. 

Let  us  return  to  the  rolling  polyhedron  and  look  at 
the  track  it  has  left  behind.  Each  piece  of  it,  formed  by 
one  side,  represents  an  elementary  species,  and  we  will 
imagine  that  all  such  species  of  a  certain  strip  of  the  path 
have  left  living  offspring.  The  question  is  where  to 
place  the  boundaries  of  a  "species"  in  such  a  group. 

Instead  of  a  discussion  I  shall  give  the  answer  which 
one  of  the  most  famous  of  the  older  systematists.  Hooker, 
has  given  in  certain  definite  cases.  First  in  regard  to 
Oxalis  corniculata.     The  forms  of  this  collective  species, 


The  Elements  of  the  Species.  59 

which  grow  in  New  Zealand,  have  been  raised  by  Cun- 
ningham into  7  well-defined  species ;  but  since  con- 
necting links  between  all  these  seven  forms  are  found  in 
different  countries  Hooker  has  united  them  into  a  single 
species.^ 

Another  good  example  is  furnished  by  Loiuaria  pro- 
cera,  a  fern  from  New  Zealand,  Australia,  South  Africa 
and  South  America.  If  we  were  acquainted  with  the 
forms  from  one  of  these  localities  only,  we  should  recog- 
nize, in  them,  a  number  of  species.  But  when  those  from 
all  these  localities  are  compared  they  form  a  complete 
series,  and  they  are  consequently  united  as  a  single  spe- 
cies. But  this  species  comprises  a  much  larger  series 
of  forms  than  all  the  remaining  species  of  Lomaria  put 
together. 

The  limits  of  collective  species  arise  therefore  by  the 
dropping  out  of  links  in  the  chain  of  elementary  species. 
These  gaps  are  apparent  when  one  confines  his  attention 
to  a  single  region;  and  real  if  they  still  persist  when  the 
Floras  of  the  world  have  been  examined.  If  the  O.valis 
corniculata  or  the  Loiuaria  procera  ceased  to  exist  in  any 
one  country  the  present  species  would  have  to  be  split 
up  into  smaller  ones. 

Or  in  other  words :  Linnean  species  arise  by  the  dis- 
appearance of  single  elementary  species  from  a  hitherto 
unbroken  series.  This  origin  is  therefore  a  purely  his- 
torical occurrence  and  can  never  become  the  object  of  ex- 
perimental investigation.^ 

^'Species"  therefore  have  very  little  physiological  sig- 

*  J.  D.  Hooker,  Introductory  Essay  to  the  Flora  of  N'e^i'  Zealand, 
1853,  p.  18.    Compare  also  Hooker's  account  of  Aconitum  Napellus. 

^  The  famous  expression  of  Spencer,  The  survival  of  the  fittest, 
is  therefore  incomplete  and  should  run  the  survival  of  the  fittest 
species. 


60 


Mutability  and  Individual  Variation. 


nificance,  whereas  the  study  of  specific  characters  will 
some  clay  form  the  most  important  branch  of  investiga- 
tion in  the  whole  domain  of  biology. 


':i^m 


P¥ 


/ 


Fig.  15.  ZeaMays  tunicata  {or  cry ptosperma) .  Three 
ears  from  a  sowing  of  seeds  from  the  same  ear. 
The  individual  seeds  are  enclosed  in  the  husks ;  in 
A  however,  incompletely  covered  about  the  middle 
of  the  ear,  and  almost  naked  at  the  top.  C  is  the 
intermediate  form ;  B  has,  especially  l3elow,  very 
large  husks. 

Continuous  Variation  of  Elementary  Specific  Char- 
acters.— The  difference  between  fluctuation  and  mutation 
perhaps  comes  out  most  clearly  in  this  connection.     By 


The  Elements  of  the  Species. 


61 


mutation  new  characters  arise  all  at  once.  Such  char- 
acters are  however  just  as  variable,  and  vary  in  the 
same  way  as  those  specific  characters  with  which  we  are 
already  familiar.^  There  are  so  many  examples  of  this 
rule  that  it  is  difficult  to  make  a  choice.-  Zea  Mays  tiuii- 
cata  or  cryptosperina  has  its  seeds  enveloped  in  husks,  but 
the  length  of  these  husks  varies  in  a  high  degree ;  some- 
times they  scarcely  cover  the  seed,  in  other  ears  they  are 


Fig.  i6.  Leaves  of  Soxifraga  crassifolia  in  various 
degrees  of  pitcher  formation,  the  succeeding  stages 
being  reoresented  by  the  figures  1-5.  This  process 
can  be  imagined  as  consisting  in  the  edges  of  the 
leaves  folding  upwards  and  fusing  together.  The 
degree  of  this  fusion  is  seen  to  be  very  variable. 

3  or  4  times  as  long,  if  not  more.  Very  often  they  are 
much  longer  in  the  lower  part  of  one  and  the  same  ear, 
than  in  the  upper;  and  their  length  gradually  decreases 
as  the  apex  of  the  ear  is  approached  (Fig.  15).  Varie- 
gated leaves,  double  flowers,  pitchers  (Fig.  16),  split 
leaves  and  so  forth  occur  in  great  variety,  and  it  would 
not  be  difficult  to  demonstrate  the  applicability  of  Oue- 

^  See  also  Intracellulare  Pangenesis,  pp.  69-70. 

^For  examples  from  the  animal  kingdom  see   Bateson,  Mate- 
rials, p.  68. 


62  Mutability  and  Individual  Variation. 

TELEXES  laws  to  these  cases.  For  each  character  there  is 
a  mean,  around  which  the  variants  are  grouped  according 
to  the  laws  of  probabihty.  In  similar  fashion,  the  split- 
ting of  the  leaves  in  Chclidoniiun  laciniatwn,  varies; 
even  glabrous  and  unarmed  varieties  exhibit  a  certain  de- 
gree of  variability  in  the  extent  to  which  they  manifest  the 
character  which  they  are  supposed  not  to  possess.  (Young 
shoots  of  Bisciitclla  laevigata  glabra,  fruits  of  Acs- 
cnlus  Hippocastaniun  incrmis,  and  so  forth.)  Five  leaved 
clover  {Trifoliiun  pratcnse  qiiinqiic folium)  varies  in  the 
number  of  leaflets  between  3  and  7 ,  obviously  following 
Quetelet's  laws.^  The  characters  peculiar  to  Papaver 
soninifcruni  polycephalum  (Figs.  27  and  28,  Chap.  IV, 
§  16)  and  Papaver  bracteatiun  monopetahim  (Fig.  1, 
p.  12)  are  in  the  highest  degree  variable.  The  same 
is  true  of  the  syncotylous  and  tricotylous  races.  The 
widest  range  of  variability  and  complete  immutability 
are  frequently  associated.^  Such  variation  or  fluctuation 
is  therefore  an  occurrence  of  quite  a  different  order  from 
mutation. 

//  §  6.  THE  MUTATION  HYPOTHESIS. 

Although  I  do  not  intend  to  discuss  the  views  of  my 
contemporaries  on  selection  and  mutation  at  large  in  this 
work,^  I  shall  now  call  attention  to  the  fact  that  ob- 
jections are  continually  being  raised  against  the  theory 
of  selection   from  all  sides. ^     The  authors  in  question 

*  Over  het  omkcercn  van  halve  Galton-ciirven,  Botanisch  Jaar- 
boek  of  the  Society  Dodonaea,  X.  Jahrg.,  1878,  p.  46. 

'Alimentation  et  Selection.  Vol.  Jubilaire  de  la  Societc  dc  Bio- 
logie  de  Paris,  Dec.  1899. 

^  For  a  critical  presentation  of  both  sides  of  the  question  the 
reader  is  referred  to  O.  Hektvvig^  Zeit-  und  Streitfragen  der  Biologie. 

*  See  also  Bateson,  Materials,  p.  567. 


The  Mutation  Hypothesis.  63 

express  themselves  more  or  less  definitely  in  favor  of 
the  mutation  hypothesis. 

E.  D.  Cope  was  the  first  to  clearly  formulate  objec- 
tions against  the  doctrine  of  selection.  Selection  pre- 
serves the  good  and  weeds  out  the  bad,  but  whence  does 
the  good  arise?  Obviously  ordinary  variability  is  not 
sufficient,  and  causes  of  an  entirely  different  kind  must 
be  sought  for.  Such  causes  he  includes  under  the  term 
bathmism. 

Carl  Semper  similarly  rejects  the  selection  theory 
and  ascribes  considerable  importance  to  the  influence  of 
the  environment,  the  so-called  monde  ambiant  of  the 
French  school,  in  originating  useful  specific  characters. 

Louis  DoLLO  was  the  first  to  express  the  view  that 
revolution  est  discontinue  from  the  standpoint  of  the 
theory  of  descent.  He  supports  his  statement  by  a  series 
of  facts,  partly  zoological,  partly  botanical,  but  especially 
derived  from  his  own  researches  in  paleontology.  He 
puts  forth  the  additional  proposition  that  revolution  est 
irreversible  et  limit ce.^ 

According  to  Wallace^s  selection  theory,  progres- 
sive change  by  artificial  and  natural  selection  is  supposed 
to  be  unlimited  and  even  reversible.  It  must  be  reversed 
according  to  Wallace  as  soon  as  the  conditions  on  which 
the  selection  depends  are  themselves  reversed.  According 
to  the  mutation  theory,  on  the  other  hand,  no  cause  can 
be  assigned  which  would  make  a  mutation  reversible, 
apart  from  the  loss  or  latency  of  characters.  Each 
mutation  is  a  definitely  circumscribed  unit. 

About  a  year  later  there  appeared  Bateson's  famous 
work   Materials   for   the   Study   of    Variation    Treated 

^  Louis  Dollo,  Lcs  Lois  dc  f  evolution.  Bull.  Soc.  Bclgc  de  Geo- 
logic, T.  VII,  p.  164,  Annee  1893. 


64  Mutability  and  Indiz'idiial  Variation. 

Especially  zvith  Regard  to  Discontinuity  in  the  Origin 
of  Species.  The  special  part  of  this  book  consists  of  an 
exhaustive  catalogue  of  instances  of  variations  in  num- 
ber, or  so-called  meristic  variations,  in  the  animal  king- 
dom. Variations  and  mutations  in  the  number  of  verte- 
brae, of  fingers,  of  joints  of  the  tarsus,  etc.,  are  set 
forth,  and  are  included  under  the  term  discontinuous 
variations.^  The  general  part  is  devoted  to  a  criticjue  of 
the  modern  theory  of  evolution.  The  theory  of  descent 
has,  according  to  Bateson^  not  merely  to  account  for 
the  kinship  of  organisms.  This  point  is  already  granted. 
But  it  also  has  to  explain  the  differences  between  indi- 
vidual forms  and,  with  regard  to  this  point,  Bateson 
asserts  with  perfect  right  that  the  species  alive  at  the 
present  day  are  sharply  and  completely  separated  from 
one  another,  and  that  transitions  between  them  either 
do  not  occur  at  all,  or  at  most,  very  seldom.  Existing 
species  form  a  discontinuous  series.  The  theory  of 
descent,  therefore,  has  to  account  not  only  for  their 
relationship,  but  also  for  this  discontinuity.^  The  latter 
forms  one  of  the  weak  points  in  the  current  theory  of 
selection.  For  according  to  this  theory,  the  series  of 
ancestors  of  any  given  organism  must  be  a  continuous 
one,  seeing  that  the  only  differences  between  parents  and 
offspring  are  of  the  so-called  individual  or  fluctuating 
kind.  Whence  then  arise  the  gaps  which  now  separate 
species  from  their  nearest  allies? 

The  usual  answer  that  is  given  is  to  point  to  the  ex- 
istence of  numerous  intermediate  forms  These  however 
are  not  transitional  forms,  but  independent  types,  namely 

*  See  especially  pp.  568  and  571 ;  also  pp.  15,  6t,  etc.  The  argu- 
ment  of  Duncker  (Biol.  Ccnfralblatt.  1899,  p.  372)^  is  therefore  not 
really  directed  against  Bateson's  use  of  the  term  discontinuous. 

^  See  pp.  5,  17,  etc. 


The  Mutation  Hypothesis.  65 

elementary  species  or  subspecies.  Bateson  expressly 
points  out  that  the  law  of  elementary  species  holds  good 
for  the  animal  as  well  as  for  the  vegetable  kingdom ; 
but  that  these  forms  have  as  yet  received  much  too  little 
attention.  Elementary  species  are  sharply  and  completely 
separated  from  one  another,  they  do  not  merge  into  one 
another,  either  in  the  wild  state,  or  under  cultivation 
(provided  that  crossing  does  not  occur). 

This  sharp  delimitation  of  the  elementary  species  is 
so  general  a  phenomenon  that  it  certainly  points  to  a  dis- 
continuous origin.  The  main  object  of  Bateson's  book 
is  to  arrange  and  collect  the  material  in  such  a  way  as 
to  give  some  insight  into  this  discontinuity.^ 

A  very  serious  objection  to  the  theory  of  selection  is 
brought  forward  by  him  in  reference  to  the  usefulness  of 
specific  characters."  It  has  been  repeatedly  asserted  by 
Darwin  and  others  that  the  characters  which  separate 
allied  species  from  one  another  are  not  of  particular  ad- 
vantage in  the  struggle  for  existence,  but  are  as  a  rule 
useless  and  inconsiderable.  Nevertheless  these  differ- 
ences are  often,  apparently,  very  complex  and  constant 
characters  but  "of  doubtful  value."  The  existence  of 
such  characters  cannot  be  accounted  for  by  Wallace^s 
theory  of  selection  which  explains  useful  characters  in 
so  beautiful  and  simple  a  manner.  The  mutation  theory, 
on  the  other  hand,  gives  a  perfectly  simple  explanation 
of  the  existence  of  such  characters ;  for  useless,  but  not 
dangerous,  mutations  must  appear  as  often  as  useful  ones, 
and  have  almost  as  much  likelihood  as  these  of  per- 
sisting. 

^  Species  are  discontinuous ;  may  not  the  variation  by  which  spe- 
cies are  produced,  be  discontinuous  too?  p.  i8.     See  also  pp.  69,568. 

^  Page  II. 


66  Mutability  and  Individual  Variation. 

Bateson's  conclusion  is  expressed  in  the  following 
words :  The  evidence  of  variation  suggests  in  brief,  that 
the  discontinuity  of  species  residts  from  the  discontinuity 
of  variation.^ 

W.  B.  Scott,  in  an  exhaustive  critique,  has  expressed 
his  opposition  to  many  of  the  views  in  Bateson's  book.- 
He  particularly  objects  to  the  statement  that  species  form 
a  discontinuous  series.  He  adduces  recent  paleontolog- 
ical  discoveries  as  proof  that  there  are  no  such  gaps  in 
the  genealogical  trees  of  the  horses  or  of  many  other 
mammals.  Such  series  are  only  discontinuous  when  our 
knowledge  concerning  them  is  incomplete.  In  contin- 
uous series  the  progression  took  place  by  almost  imper- 
ceptible gradations.^  These  gradations  seem,  however, 
to  be  what  Bateson  calls  steps.  Let  us  return  to  the 
simile  of  Galton's  rolling  polyhedron.  The  question 
whether  we  choose  to  call  this  movement  continuous  or 
discontinuous  depends  on  our  point  of  view.  Even  a 
series  of  numbers  can  be  unbroken  and  therefore  con- 
tinuous. 

The  word  mutation  has  been  used  more  in  paleon- 
tology than  in  other  sciences  to  express  the  differences 
between  allied  species.  The  actual  process  of  mutation, 
the  change  of  one  species  into  another,  can  obviously 
not  form  a  problem  of  paleontology.  The  paleontol- 
ogist can  only  study  the  series  of  consecutive  forms. 
From  such  series  however  important  information  may  be 
derived  as  to  the  size  of  individual  steps,  that  is  to  say, 
the  mutations.  Waagen  has  said  that  the  more  com- 
plete the  geological  evidence  is  the  less  perceptible  do 

'^  Loc.  cit.,  p.  568. 

"W.  B.  Scott,  On  Variations  and  Mutations.     Am.  Journ.  Sci., 
8°  series,  vol.  48,  Nov.  1894,  PP-  355-374- 
^  Page  360. 


The  Mutation  Hypothesis.  67 

the  specific  gradations  become.^  We  can  obviously  never 
know  how  much  more  numerous,  if  at  all,  the  mutations 
have  been  than  the  species  whose  remains  we  find ;  count- 
less species  may  have  arisen  without  leaving  a  trace 
behind,  but  whether  this  is  the  result  of  the  struggle 
for  existence,  of  natural  selection,  or  of  an  advance  in 
a  predetermined  direction,  cannot  now  be  ascertained. 
Phylogenetic  changes  make  straight  for  the  goal,  seldom 
swerving  to  the  side,  hardly  ever  advancing  in  a  zigzag 
line,^  but  whether  natural  selection  or  variation  in  a 
definite  direction  was  the  determining  cause  is  obviously 
a  matter  of  personal  opinion. 

The  constancy  of  forms  arising  by  mutation,  as  op- 
posed to  fluctuating  variability,  is  supported  by  the  re- 
sults of  paleontological  research.  Waagen  as  well  as 
Scott  and  others  have  declared  against  Wallace^s  se- 
lection theory  on  these  grounds.  They  strongly  maintain 
that  mutations  must  be  admitted  to  a  more  prominent 
place  in  any  theory  of  evolution.^  Each  ''mutation" 
(elementary  species)  serves  as  a  new  center  of  analogous 
variations. 

'  Scott  deduces  from  paleontological  data  a  further 
series  of  conclusions  relative  to  the  occurrence  of  muta- 
tions. I  find  many  of  these  views  supported  by  a  critical 
study  of  the  theory  of  variation  as  well  as  by  my  own 
experimental  work.  I  shall  have  to  return  to  them  at 
the  conclusion  of  tliis  section,  and  in  the  first  chapter 
of  the  following  one. 

Last  year  Korschinsky  definitely  expressed  himself 
as  opposed  to  the  present  form  of  the  selection  theory. 

^Waagen,  Benecke's  Geogr.  PaVdontol.  Beitrage,  II,  S.  170. 
*  Scott,  loc.  cit.,  p.  370. 
^  Loc.  cit.,  pp.  372,  27Z- 


68  Mutability  and  Individual  Variation. 

He  includes  mutations  or  spontaneous  variations  under 
the  term  heterogenesis  on  the  analogy  of  Kolliker^s 
heterogenetic  reproduction  and  the  "Heterogenism"  of 
Hartmann.^  He  bases  his  conclusions  on  the  data  of 
horticultural  practice  and  gives  a  complete  and  very  im- 
portant survey  of  the  cases  in  which  the  history  of  the 
first  appearance  of  varieties  is  more  or  less  accurately 
known,  or  in  which  the  occurrence  of  new  forms  other 
than  by  a  series  of  transitional  stages  points  to  a  sudden 
origin. 

Such  heterogenetic  changes  (the  mutations  of  the 
older  investigators)  can  be  progressive  or  retrogressive, 
that  is  the  organs  can  become  more  complicated  or  more 
simple ;  both  kinds  of  changes  must  often  happen,  but 
the  retrogressive  ones  can  obviously  occur  more  easily 
than  progressive  ones.  Mutations  can  be  induced,  as 
Darwin  also  believes,  by  the  cumulative  operation  of 
favorable  conditions  during  development  and  by  rich 
nutrition  continued  through  many  generations.  Forms 
that  have  newly  arisen  can  sometimes  be  so  sharply  dis- 
tinguished from  the  parent  type  that  any  systematist 
would  take  them  for  a  separate  species  if  he  did  not  know 
their  origin. 

Korschinsky  concludes  from  a  survey  of  the  facts 
at  his  disposal  that  among  garden  plants  all  new  forms, 
or  more  strictly  all  new  characters,  have  originated  by 
heterogenesis.  New  varieties  are  not  obtained  in  horti- 
culture by  the  selection  or  cumulation  of  individual  differ- 
ences.    Selection  is  a  conservative  agency.     It  fixes  new 

^  S.  Korschinsky,  Heterogenesis  und  Evolution,  Naturzvissen- 
schaftlichc  Wochenschrift,  1899,  Vol.  XIV,  No.  24.  A  larger  work 
appeared  in  the  Mcmoircs  of  the  St.  Petersburg  Academy  of  Sciences, 
1899,  Vol.  IX.  See  also  Flora,  Vol.  59,  1901,  pp.  240-363.  (Note 
of  1908). 


The  Mutation  Hypothesis.  69 

characters  that  have  ah-eady  arisen  but  it  cannot  of  itself 
produce  new  forms. 

This  author  then  proceeds  to  a  comparison  of  the 
fundamental  principles  of  the  selection  and  mutation  the- 
ory. As  a  result,  he  finds  that  the  theory  that  species 
have  originated  by  the  selection  of  individual  differences 
is  beset  with  series  difficulties,  whereas  the  belief  that 
this  has  taken  place  by  mutations  (heterogenetic  varia- 
tions) provides  us  with  a  satisfactory  explanation  or  at 
any  rate  is  in  close  accord  with  the  facts.  Two  facts  that 
strongly  favor  this  view  are  (1)  the  absence  of  transi- 
tional forms  and  (2)  the  existence  of  at  least  apparently 
useless  characters. 

Darwin's  view  is  that  the  probability  of  a  progressive 
development  in  animals  and  plants  is  great  in  proportion 
to  the  severity  of  the  struggle  for  existence.  Kor- 
SCHINSKY  on  the  other  hand  holds  that  favorable  con- 
ditions afford  the  best  opportunity  for  the  appearance 
of  mutations.  For  the  new  forms  in  order  to  establish 
themselves  require  suitable  opportunity  for  the  develop- 
ment of  their  powers  and  fertility  to  the  full.  It  will 
be  seen  that  this  contrasts  strongly  with  Darwin's  view, 
which  is  that  the  innumerable  weaker  variants  simply 
cease  to  exist  while  the  rarer  stronger  ones  survive. 

I  shall  now  close  this  historical  sketch.  I  hope,  at  a 
later  date  to  review  more  fully  the  views  of  modern 
authors;  it  will  then  be  seen  that  the  general  opinion  is 
that  the  theory  of  selection  is  unsatisfactory.  For  exam- 
ple DuNCKER  says  that  individual  variability  is  static 
rather  than  kinetic;  and  therefore  does  not  provide 
material  for  natural  selection.^  Lord  Salisbury  said 
in  his  presidential  address  at  the  meeting  of  the  British 

^  Biolog.  Centralhlatt,  1899,  p.  2,72- 


70  Mutability  and  individual  Variation. 

Association  in  Oxford  in  1894:^  The  theory  of  selection 
is  by  no  means  to  be  regarded  as  proven ;  for  a  host  of 
difficulties  stand  in  the  way  of  the  acceptance  of  the 
explanation  of  evolution  by  the  accumulation  of  ordi- 
nary (individual)  variations.  And  still  more  recently 
Rosa,-  from  the  standpoint  of  critical  studies  in  phy- 
logeny  has  insisted  on  the  distinction  between  mutations 
and  fluctuations,  considering  only  the  first  group  as 
phylogenetic  variations. 

^Nature,  Aug.  9,  1894. 

^D.  Rosa,  La  ridii.zionc  progressiva  dcUa  variabilita  c  i  suoi 
rapporti  coll'estinaione  et  coU'originc  dclle  specie,  Torino,  C.  Clau- 
sen, 1899,  P-  93- 


in  SELECTION  ALONE  DOES  NOT  LEAD  TO 
THE  ORIGIN  OF  NEW  SPECIES. 

§  7.  SELECTION  IN  AGRICULTURE  AND  HORTICULTURE. 

Botanical  literature  affords  very  few  instances  of 
scientific  experiments  on  artificial  selection.  And  so  long 
as  this  continues  to  be  the  case  we  shall  be  thrown  back 
on  the  experience  of  breeders. 

One  of  the  best  scientific  experiments  of  this  kind 
is  Fritz  Mueller's  on  Selection  in  Maize.  ^  He  dealt 
with  the  number  of  rows  on  the  ears  (Fig.  17)  and 
started  by  choosing  the  ears  with  the  greatest  number 
of  rows  for  sowing;  the  commonest  were  those  with 
10-12  rows;  the  others  group  themselves  round  this  fig- 
ure in  familiar  fashion  according  to  Quetelet's  laws. 
Among  many  thousands  of  ears  a  single  one  was  found 
with  18,  but  none  with  20  rows.  At  the  end  of  three 
years  selection  the  mean  had  shifted  to  16  rows,  while 
single  ears  had  as  many  as  26  rows. 

I  have  repeated  this  experiment  over  a  longer  series 
of  vears,  and  have  exhibited  the  result  in  the  form  of  a 
genealogical  tree,  plotting  the  variability  by  the  fan 
method  as  explained  in  Fig.  13,  p.  52.  The  fans  have  been 
reduced  by  substituting  the  most  essential  lines  for  the 
numerous  triangles  of  Fig.  13.    The  middle  line  of  each 

^Kosmos,  i886,  Vol.  II,  p.  22. 


72      Selection  Does  Not  Lead  to  Origin  of  Species. 

fan  corresponds  to  the  mean  (the  apex  of  the  curve), 
the  two  dotted  Hnes  to  the  quartiles  Q  and  Qi ;  between 
which  therefore  He  that  half  of  all  the  individuals  coming 
nearest  to  the  average.  The  two  outer  lines  of  each  fan 
denote  the  ears  with  the  greatest  and  smallest  observed 
number  of  rows;  their  divergence  is  of  course  largely 


m^ 


m'^:-- 


Fig.  17.  Zca  Mays.  Ears  with  8,  16  and  22  rows  of 
seeds  from  my  experiment  in  selection  carried  out 
from  1 886- 1 894. 


dependent  on  the  size  of  the  harvest ;  this  amounted  on 
the  average  to  about  200  ears  a  year. 

Of  the  two  lines  going  from  top  to  bottom  the  right- 
hand  one  represents  the  numbers  of  rows  on  the  ears 
actually  chosen  for  sowing.  That  is  to  say  there  were 
sown  seeds  from  ears  with  16  (1887),  20,  20,  24,  22, 
22,  and  22  rows ;  ears  with  a  greater  number  of  rows 


Selection  in  Agriculture  and  Horticulture.         73 

were  usually  too  poor  in   seeds  to  be  of  any  use   for 
continuing  the  experiment. 


i        ?o       »        n        K        19       20        it        ?♦       te        u 


1S9i 


1893 


1392 


1391 


1S89 


ias8 


1SS7 


1886 


8  10  12  1h  16  IS  20 


2if  2t> 


Fig.  i8.  Pedigree  of  an  Experiment  in  Selection  with 
Maize.  The  numbers  at  the  top  and  bottom  of  the 
figure  show  the  number  of  rows  in  the  ear.  The 
experiment  began  in  1887 ;  the  hnes  for  1886  give 
the  characters  of  the  race  with  which   I  started. 


The  left-hand  line  joins  the  ends  of  the  middle  rays, 
which  correspond  to  the  apices  of  the  curves  for  each 


74      Selection  Docs  Not  Lead  to  Origin  of  Species. 

year.  It  shows  us  therefore  the  mean  progress  of  the 
yield.  This  hue  comes  closer  every  year  to  that  of  the 
ears  used  for  seed.  A  proper  study  of  its  course  would 
have  necessitated  the  undertaking  of  effecting  artificial 
self-fertilization  which  in  the  case  of  maize  is  known 
often  to  lead  to  a  poor  harvest.  I  should  have  preferred 
to  have  used  another  plant,  had  not  the  ears  of  maize 
lent  themselves  so  admirably  to  a  demonstration  of  this 
kind. 

It  is  not  necessary  to  repeat  that  the  experience  of 
breeders  provided  the  main  support  for  Darwin's  selec- 
tion theory.  In  its  broad  outlines  the  process  of  natural 
selection  is  like  that  of  artificial  selection.  But  as  soon 
as  we  come  to  dissect  the  component  factors  of  these 
processes  we  encounter  serious  difficulties,  as  I  have  al- 
ready remarked  in  the  Introduction. 

The  chief  cause  of  this  state  of  affairs  is  to  be  sous^ht 
in  the  circumstance  that  breeders  rarely  work  with  single 
characters  but  have  as  a  rule  aimed  at  improving  their 
plants  in  every  possible  respect, 

They  never  attempt  a  separation,  or  even  a  separate 
observation,  of  special  characters.  The  second  cause  is 
that  breeders  have  no  interest  in  distinguishing  between 
their  different  methods  of  improving  their  plants.  On 
the  contrary  it  is  usually  the  best  plan  to  allow  the  various 
methods :  of  the  choice  of  desirable  mutations,  of  their 
gradual  improvement  by  repeated  selection,  of  natural 
or  artificial  crossing,  of  manuring  and  what  not,  to  exert 
their  combined  effect. 

The  breeder  is  only  interested  in  the  result.  The 
means  by  which  this  has  been  attained  is  a  secondary 
matter  and  is  seldom  thought  worthy  of  an  accurate 
record. 


Selection  in  Agriculture  and  Horticulture.         75 

In  choosing  cases  for  the  scientific  study  of  the  pro- 
cess of  selection  it  is  of  the  highest  importance  to  ex- 
ckide  all  those  in  which  crossing  has  taken  place,  or  where 
it  has  not  been  excluded  with  absolute  certainty.  Many 
genera  and  species  owe  their  present  range  of  forms 
(which  is  what  breeders  call  variability)  almost  entirely 
to  the  repeated  crossings  between  the  original  wild  forms 
that  w^ere  introduced,  whether  these  were  different  Lin- 
nean  species  or  numerous  elementary  species  of  such. 

There  are  two  chief  categories  to  be  distinguished. 
First  there  are  those  genera  in  which  a  very  wide  range 
of  form  is  desired,  and  for  this  purpose  almost  every 
conceivable  cross  between  the  different  varieties  has  been 
carried  out.  The  best,  either  from  the  utilitarian  or 
from  the  decorative  point  of  view,  are  then  put  on  the 
market  and  are,  in  the  eyes  of  the  layman,  an  inscrutable 
medley.  Fuchsias,  dahlias,  chrysanthemums,  wheat  and 
potatoes  are  the  best  known  examples.  The  novelties 
of  the  breeders  arise  in  these  cases  almost  without  ex- 
ception by  the  deliberate  combination  of  characters  al- 
ready existing  in  the  old  types. 

Secondly  there  are  the  genera  which  have  developed 
in  a  definite  direction  since  the  beginning  of  their  culti- 
vation, e.  g.,  begonia,  gladiolus,  caladium,  amaryllis, 
canna  and  many  others.  The  improvement  in  these 
cases  has  almost  always  been  the  result  of  the  discovery 
of  new  wild  species.  These  have  been  crossed  with  the 
cultivated  bastard  race  and  in  this  way  the  desired  char- 
acters of  the  former  have  been  transferred  to  the  latter. 
The  large  and  beautiful  blossoms,  the  caladiums  with 
variegated  leaves,  the  hardy  gladioli  etc.  have  been  got 
in  this  way.  The  characters  of  the  new  varieties  already 
existed  in  nature,  distributed  between  the  different  spe- 


76      Selection  Docs  Not  Lead  to  Origin  of  Species. 

cies.  The  combinations  are  new  in  cultivation ;  but  the 
characters  themselves  do  not  owe  their  origin  to  it. 

Of  course  I  do  not  deny  the  appearance  of  mutations 
in  cultivation,  but  so  far  as  1  have  been  able  to  learn 
personally  from  the  best  known  breeders  these  are  rela- 
tively rare  occurrences. 

It  is  impossible  to  insist  too  much  that  the  much 
talked  of  progress  in  cultivation  is  a  delusion  if  the  part 
played  by  crossing  is  left  out  of  account  or  if  the  results 
of  this  crossing  are  regarded  as  the  effect  of  selection. 
And  this  happens  only  too  often.  Hybridization  is  so 
much  more  certain  and  easy  a  way  than  selection  of  get- 
ting something  new  that  breeders  would  nearly  always 
be  working  against  their  own  interests  if  they  did  not 
expose  their  plants  as  freely  as  possible  to  natural  cross- 
fertilization.  The  possibility  of  crossing  should  evi- 
dentlv  onlv  be  excluded  when  we  are  concerned  with  the 
fixation  of  races  or  with  methodical  selection  carried  out 
according  to  strict  principles.  But  it  is  only  experiments 
of  this  kind  that  have  any  value  for  the  theory  of  selec- 
tion. Unfortunately  they  are  much  more  rarely  carried 
out,  or  at  least  more  rarely  described  than  one  could 
wish. 

Most  of  the  brief  notes  made  by  breeders  on  varia- 
bility, which  is  apparently  considerable,  are  open  to  the 
objection  that  the  seeds  in  question  have  been  collected 
from  plants  fertilized  by  the  wind  or  by  insects.  And  if, 
for  example,  we  read  through  the  mass  of  material  col- 
lected by  Darwin,  with  this  in  mind,  we  shall  find  that 
much  that  seemed  to  be  variability  or  mutability  receives 
a  much  simpler  explanation  by  supposing  that  it  was  the 
result  of  crossing  or  of  the  collection  of  seeds  from 
hybrid  plants.     It  will  always  be  found  that  the  number 


Selection  in  Agriculture  and  Horticulture.         77 

of  cases  of  alleged  variability  in  plants  whether  in  the 
wild  or  cultivated  state  suffers  a  considerable  shrinkage 
so  soon  as  one  views  the  individual  statements  from  the 
point  of  view  of  possible  chance  crossings.^ 

I  maintain,  in  a  word,  that  much  that  has  up  to  now 
been  alleged  as  evidence  of  variability  overstepping  the 
limits  of  elementary  species  (that  is  mutability)  should 
really  be  attributed  to  the  result  of  unobserved  chance 
crossings." 

It  is  worth  while  to  draw  attention  to  the  further 
distinction  between  agricultural  and  horticultural  selec- 
tion. For  a  clear  perception  of  the  relations  existing 
between  them  w^ill  facilitate  our  understanding  of  the 
difference  between  fluctuations  and  mutations. 

Every  year  there  are  put  on  to  the  market  by  pro- 
fessional gardeners  a  certain  number  of  so-called  novel- 
ties especially  of  plants  propagated  by  seeds,  for  it  is 
these  that  I  have  particularly  in  view.^  They  are  partly 
hybrids,  partly  really  new  varieties  and  subspecies,  partly 
species  brought  from  foreign  lands.  The  varieties  and 
subspecies  arise  suddenly  and  only  a  few  individuals  of 
them  occur  as  a  rule.  They  seldom  appear  in  the  nursery 
gardens  but  usually  in  those  of  customers,  whose  total 
area  is  of  course  much  greater  than  that  of  the  firms 
which  supply  the  seeds,  and  where  as  a  rule  much  more 
time  and  attention  is  devoted  to  the  individual  plants. 

*  See  also  Hoffmann,  Botanische  Zcitung,  1881,  p.  381.  "The 
seeds  of  isolated  flowering  examples  have  shown  no  tendency  to  the 
formation  of  variations." 

^  In  a  later  section  T  propose  to  deal  with  this  comparison  ex- 
haustively and  from  the  point  of  view  of  careful  experiment. 

^  The  commercial  aspect  of  breeding  has  been  most  thoroughly 
gone  into  by  C.  Fruwirth,  Ziichtungsbcstrehiingcn  in  den  Vcreinig- 
icn  Staaten,  in  Fuhling's  Landzvirthsch.  Zeitung,  1887,  Jahrg.  s^^ 
p.  16. 


78      Selection  Does  Not  Lead  to  Origin  of  Species. 

The  nurserymen  then  usually  buy  the  novelties  from  the 
customers  in  question  at  a  considerable  price.  As  a  rule 
4  or  5  years  elapse  before  such  a  novelty  is  put  on  the 
market.  During  this  time,  so  we  are  told,  it  has  been 
made  constant  by  selection.  It  would  be  more  correct 
to  say  that  they  are  freed  from  the  adulterating  effects 
of  free  crossing.  For  the  selection  consists  in  weeding 
out  the  so-called  rogues  at  the  time  of  flowering  (sup- 
posing that  we  are  dealing  with  flowering  plants)  in  order 
to  save  seed  only  from  the  pure  individuals.  But  if  we 
are  dealing  with  vegetables  the  selection  takes  place  long 
before  they  are  in  flower,  so  that  there  is  no  danger  of 
crossing  in  this  case. 

These  rogues  are  nothing  more  than  hybrids  resulting 
from  free  crossing  in  the  preceding  summer.  I  have 
often  had  the  opportunity  of  watching  this  weeding  out. 
It  takes  place  at  the  height  of  the  flowering  season.  The 
pure  individuals  may  therefore  have  been  already  partly 
fertilized  by  the  rogues ;  and  for  this  reason  some  of  the 
seed  for  the  next  year  may  have  been  contaminated. 
The  sole  object  of  the  selection  is  to  reduce  the  mixture 
with  other  forms  to  a  minimum ;  the  pollination  is  left  to 
insects  from  the  first  generation  onwards,  so  that  cross- 
fertilization  always  takes  place.  I  have  never  been  able 
to  find  that  in  ordinary  cases  selection  had  any  other 
object  than  the  purification  of  the  new  race  from  the 
effects  of  mixed  ancestry. 

The  use  the  gardener  makes  of  his  4  or  5  years  is 
to  increase  his  stock  of  seed  suflicientlv  to  make  it  worth 
while  to  put  it  on  the  market.  This  is  in  fact  a  far  more 
important  matter  than  the  process  of  purification  that  we 
have  been  speaking  of.  As  soon  as  the  requisite  quantum 
of  seed  is  obtained  it  is  put  on  the  market.     Absolute 


Selection  in  Agriculture  and  Horticulture.         79 

purity  is  not  guaranteed.  I  have  often  bought  seeds 
of  novelties  and  tested  their  purity  by  extensive  sowings. 
They  almost  always  contain  impurities.  But  whenever 
I  fertilized  some  specimens  of  the  new  forms  with  their 
own  pollen  after  taking  care  that  the  visits  of  insects 
were  excluded,  they  came  absolutely  true  in  the  next 
generation.  We  all  know  that  we  are  lucky  if  we  get  a 
purity  of  97-99%  ;  the  remaining  1-3%  are,  we  are  told, 
atavists;  as  a  matter  of  fact  they  are  practically  always 
the  survivors  of  the  impurities  that  owed  their  origin 
to  free  crossing  in  the  field. 

The  whole  profit  on  a  novelty  must  be  made  during 
the  first  year  of  its  appearance  in  the  trade.  ^  For  as  soon 
as  it  bears  seed  in  other  gardens  its  originator  loses  the 
monopoly  of  it.  For  this  reason  novelties  are  usually 
offered  for  sale  towards  the  end  of  the  year  in  special 
price  lists  to  as  many  seedmen  as  possible ;  they  introduce 
them  into  their  catalogues,  and  that  is  why  one  usually 
finds  that  most  novelties  are  put  on  the  market  simul- 
taneously by  numerous  firms.  Their  price  is  at  first  con- 
siderable, but  in  a  few  years  sinks  to  the  normal,  for  by 
that  time  as  much  seed  as  wanted  can  be  produced 
everywhere.   \^ 

A  horticultural  novelty,  when  it  has  once  arisen  and 
has  been  freed  from  the  results  of  crossing  and  put  in 
sufficient  quantity  on  the  market,  is  everybody's  plant. 
All  that  remains  to  be  done  to  keep  them  constant  is  to 
avoid  foreign  pollen. 

The  case  of  agricultural  varieties,  on  the  other  hand, 
is  quite  different.  I  am  referring  now  only  to  the  gen- 
uine improved  races  and  give  the  description  of  their  pro- 

*I  have  often  heard  the  vaUie  of  such  a  novelty  set  at  iioo  to 
£150. 


80      Selection  Does  Not  Lead  to  Origin  of  Species. 

duction  according  to  the  now  current  views.  ^  They  do  not 
arise  by  chance,  they  are  not  the  resuh  of  rare  and  sudden 
variations.  The  material  out  of  which  they  are  made  is 
furnished  by  fluctuating  variabihty.  At  the  outset,  the 
breeder  seeks  in  his  fields  for  those  plants  which  seem 
the  best  for  his  purpose,  and  collects  their  seeds  sep- 
arately. These  plants  differ  very  little  in  the  eyes  of  a 
layman  from  the  other  specimens  in  the  field.  He  sows 
seeds  from  these  on  a  small  scale,  working  every  year 
on  the  same  principles,  in  this  w^ay  gradually  increasing 
the  deviations  from  the  original  form  in  the  desired 
direction. 

He  has  as  a  rule  one  or  two  qualities  chiefly  in  view, 
but  pays  attention  where  possible  to  all  other  characters. 
He  is  not  concerned  with  the  improvement  of  one  par- 
ticular quality.  To  achieve  this  many  things  are  neces- 
sary, patience,  an  intimate  acquaintance  with  the  species 
of  plants  in  question,  and  a  firm  and  clear  conception 
of  the  ideal  to  which  he  wishes  his  race  to  attain.  And 
in  spite  of  the  possession  of  these  qualifications  the  best 
known  breeders  are  by  no  means  successful  with  every 
experiment ;  the  greatest  of  them,  that  is  those  who  have 
introduced  the  most  widely  distributed  races,  liave  often 
only  brought  out  one  or  at  most  a  very  few  successful 
novelties. 

The  value  of  such  a  race  gradually  increases.  At 
first  as  seed  for  one's  own  purpose,  but  soon  as  seed  for 
the  market.  But  the  seed  is  not  put  on  the  market  in  a 
single  year  but  gradually  during  the  period  of  improve- 
ment and  multiplication.     The  improved  characters  de- 

^  For  the  earlier  constant  products  of  selection,  e.  g.,  those  of 
Patrick  Shirreff,  and  for  my  own  views  concerning  the  description 
given  in  the  text  see  the  conckision  of  §  12,  pp.  109  ff.  and  §  23,  pp. 
178  ff.     (Note  of  1908.) 


Selection  in  Agriculture  and  Horticulture.         81 

teriorate  as  soon  as  the  new  race  is  cultivated  on  a  large 
scale,  on  account  of  the  consequent  cessation  of  rigid 
selection.  The  harvest  has  therefore  less  value  than  the 
original  sample  of  seed.  In  this  vv^ay  the  breeder  is 
assured  the  monopoly  of  his  prize  for  many  years  until, 
may  be,  his  race  is  superseded  by  another  and  a  better 
one. 

The  work  done  and  the  profits  made  by  the  horticul- 
turist are  insignificant  compared  wnth  those  of  the  agri- 
culturist. The  former  introduces  a  few  novelties  into 
the  garden  every  year.  The  latter  increases  the  yield  of 
whole  countries.  I  have  often  heard  farmers  speak  with 
pride  of  their  results  as  compared  with  those  of  gar- 
deners. 

Finally  I  would  mention  a  good  example  of  the  dif- 
ference in  question.  Beseler  in  Anderbeck  by  years  of 
patient  work  improved  his  oats  to  such  an  extent  that 
he  was  able  to  put  them  on  the  market  under  the  name  of 
Anderbecker  Oats.  This  form  was  bearded,  a  feature 
which  was  found  fault  with  from  many  quarters,  and 
prejudiced  its  sale.  It  was  a  small  matter  to  make  Ander- 
becker Oats  beardless,  provided  that  beardless  examples 
could  be  found.  This  happened  to  be  the  case ;  and  since 
that  time  Beseler's  oats  have  been  beardless.^ 

This  difiference  between  the  practice  of  agricultural 
and  horticultural  breeding  has  in  my  opinion  been  largely 
responsible  for  the  present  form  of  the  scientific  theory 
of  selection.  That  which  can  onh^  be  achieved  by  a  few 
and  at  the  cost  of  great  sagacity  and  patience,  produces 
a  great  impression ;  that  which  chance  can  put  into  the 
hands  of  any  one,  makes  none  at  all.  And  so  it  comes 
about  that  the  former  method  has  loomed  much  larger 

*v.  RiJMKERj  Getreidezuchtung,  1889,  pp.  60,  75,  and  94 


S2      Selection  Does  Not  Lead  to  Origin  of  Species. 

in  our  discussions  on  the  origin  of  species,  whilst  the 
latter  has  been  relatively  neglected.  But  it  must  not  be 
forgotten  that  the  agricultural  improved  races  do  not 
possess  the  constancy  of  true  species  •}  whereas  the  vari- 
eties and  subspecies  of  the  horticulturist  can  only  be 
distinguished  from  true  species  historically  and  systemat- 
ically— not  experimentally. 

In  conclusion :  we  see  that  in  estimating  the  value  of 
the  experience  of  breeders  for  scientific  purposes  we  have 
to  fix  our  attention  on  the  simplest  processes.  Every- 
thing that  can  be  considered  the  direct  or  indirect  result 
of  crossing  must  be  excluded  before  we  consider  its  bear- 
ing on  the  theory  of  mutation  or  selection.  Furthermore 
one  must  sharply  distinguish  between  the  races  that  have 
been  produced  by  continued  selection,  and  the  constant 
forms  which  owe  their  oriHn  to  a   sudden   fortuitous 


'fc.' 


change. 

In  horticulture  varieties  arise  by  mutations,  and  vari- 
eties are  elementary  species.  In  agriculture  according  to 
the  current  view  and  excepting  in  the  instances  of  the 
unconscious  isolation  of  elementary  species,  the  highly 
improved  races  arise  gradually  through  selection,  but  they 
never  become  species. 

§  8.  SELECTIVE  BREEDING  FOLLOWED  BY  VEGETATIVE 

PROPAGATION. 

We  shall  now  proceed  to  deal  with  the  scientific  sig- 
nificance of  selection  in  those  cases  in  which  its  products 
are  multiplied  vegetatively. 

*  Or  if  they  do  prove  to  be  constant,  they  usually  turn  out  to  be 
the  result  of  the  unconscious  isolation  of  elementary  species ;  com- 
pare Nilsson's  results,  described  in  §  12,  pp.  114  ff  and  Archiv  fiir 
Rasscnbiologie,  April  i,  1906.     (Note  of  1908.) 


r 


Selective  Breeding  and  Vegetative  Propagation.    83 

Properly  speaking  these  cases  have  no  significance 
for  the  theory  of  descent.  But  they  are  so  much  more 
striking  than  the  results  of  selection  in  seedplants  that 
they  are  often  used  as  examples. 

If  after  extensive  sowing,  or  after  repeated  selection 
of  any  species  one  gets  a  single  example  with  large 
flowers  or  fruits  or  with  any  desirable  character  in  an 
exaggerated  degree  there  are  two  possibilities. 

First  one  may  be  dealing  with  a  seedplant,  that  is  with 
a  species  which  can  either  be  propagated  only  by  seed, 
or  in  which  it  is  usual  to  propagate  it  in  this  way  in 
practice. 

Secondly,  one  may  be  dealing  with  a  plant  which  is 
capable  of  vegetative  propagation  whether  by  division 
of  the  rhizom,  by  cuttings,  by  grafting,  by  tubers,  or  by 
any  of  the  other  ways  in  which  this  may  be  effected. 

In  the  first  case  the  seeds  conform  to  the  law  of  re- 
gression. This  was  recognized  by  Vilmorin  and  after- 
wards scientifically  studied  by  Galton.  If  we  regard 
Galton's  formula  as  generally  true  the  mean  of  the 
offspring  deviates  from  the  mean  of  the  type  in  such  a 
way  that  it  retains  only  a  third  of  the  deviation  of  the 
parent.  So  that  to  produce  a  given  advance  in  the  whole 
family  we  should  have  to  sow  seed  from  a  plant  which 
had  advanced  three  times  as  far. 

To  make  the  meaning  of  this  regression  clear  I  will 
select  as  an  example  a  culture  of  Madia  elegans.  The 
mean  number  of  ray-florets  on  a  flower  head  is  21. 
and  the  other  numbers  are  grouped  round  this  in  accord- 
ance with  Quetelet's  law.  In  the  1892  crop  of  my  ex- 
periment the  mean  was  21  and  the  variation  lay  between 
16-25  ;  of  these  I  chose  6  examples,  each  possessing  16-19 
rays  in  the  terminal  head.     From  their  seeds  T  obtained 


84      Selection  Does  Not  Lead  to  Origin  of  Species. 

a  series  in  1893  varying  between  12  and  22  and  with 
a  mean  of  19  rays.  I  now  chose  the  seed  from  13-rayed 
plants  and  got  in  1894  a  generation  varying  between  13 
and  22  and  with  a  mean  of  18.  The  regression  amounted 
in  this  experiment  to  about  % ;  that  is  to  say  the  children 
deviated  only  one-third  as  much  from  the  type  of  their 
species  as  their  parents  did.^ 


1S0<t 

A 

^ 

P^ 

r 
^ 

^ 

1S93 

\ 
\ 

\ 

X 

X 

y 

/ 

/ 

/ 

1892 

\ 

\ 

■^ 

\ 

/ 

/ 

/ 

12      13      n      J.i      16      77      IS      19      20     V      2i     :'J      2*     2S 


Fig.  19.  Madia  elegans.  Successive  generations 
showing  the  result  of  the  selection  of  examples 
with  the  smallest  number  of  ray-florets.     The  fig- 

'  ures  at  the  base  of  the  ordinates  give  the  number 
of  these  florets.  The  limit  of  the  variation  fan  for 
1904  coincides  on  the  left  side  with  the  13  rays 
ordinate. 


On  the  other  hand  a  character  perpetuates  itself  un- 
altered or  almost  so  if  the  plant  bearing  it  is  propagated 
vegetatively.  The  descendants  are  of  course  nothing 
more  than  parts  of  the  original  plant ;  the  products  of  a 
single  seed.  Hundreds  or  even  thousands  of  them  can 
be  put  on  the  market,  but  together  they  constitute  merely 
parts  of  a  single  individual. 

The  whole  so-called   variety,    thus,   consists   in   this 

See  also  the  pedigree  of  my  experiment  with  maize  on  p.  y^. 


Diiratiofi  of  the  Process  of  Selection.  85 

case  of  a  single  individual.  This  is  true  in  the  case  of 
apples  and  pears  and  many  other  fruit  trees;  of  tulips 
and  other  bulbs,  of  dahlias,  canna  and  so  forth.  Among 
agricultural  plants  it  is  true  of  potatoes,  among  plants 
from  tropical  countries,  of  bananas  and  of  sugar  cane 
and  so  forth. 

Strictly  speaking  a  variety  of  this  kind  cannot  be 
compared  with  that  of  a  plant  propagated  by  seed.  It 
is,  on  the  contrary,  analogous  to  the  single  plants  chosen 
to  furnish  seed  for  market  stock.  If  we  assume  Gal- 
ton's  formula  to  be  applicable  to  this  case  also  we  may 
say  that  the  results  of  selection  are  three  times  as  great 
when  the  plants  are  propagated  vegetatively  as  when 
they  are  propagated  by  seed. 

So  that,  if  we  adduce  the  splendid  flowers  of  our 
bulbs,  the  size  of  our  potatoes  and  the  excellence  of  our 
fruit  as  examples  of  a  high  degree  of  variability  and 
of  the  perfection  that  can  be  attained  by  selection  we 
must  never  forget  that,  in  the  light  of  what  we  now  know 
on  this  head,  the  improvement  would  have  to  be  dimin- 
ished by  %  if  the  results  were  to  be  applied  to  the  theory 
of  descent.  And  if  we  do  make  this  reservation  nothing 
much  is  left,  from  the  biological  standpoint  at  any  rate. 

§  9-    ON  THE  DURATION  OF  THE  PROCESS  OF  SELECT- 

TION. 

The  modern  theory  of  selection  rests  on  two  unproved 
hypotheses : 

1.  The  advance  brought  about  by  selection  may  in- 
crease for  an  indefinite  period. 

2.  The  result  of  selection  can  become  independent 
of  selection. 


86      Selection  Does  Not  Lead  to  Origin  of  Species. 

The  experience  of  breeders  stands  in  direct  contra- 
diction to  both  these  hypotheses. 

Let  us  examine  these  statements  separately.  We  may 
consider  the  first  under  two  headings  according  as  the 
period  in  question  refers  to  the  future  or  to  the  past; 
that  is  whether  we  are  concerned  with  explaining  a  form 
already  existing,  or  with  predicting  its  possible  changes. 

Let  us  begin  with  the  past.  These  changes  have 
been  the  result  of  some  looo  years  of  domestication  and 
selection,  says  Wallace.^  And  Darwin  said,  as  a  result 
of  a  criticism  of  Hoffmann^  "Perhaps  hundreds  of  gen- 
erations of  exposure  are  necessary.''^  And  in  another 
place,  '7  cannot  doubt  that  during  millions  of  generations 
individuals  of  a  species  will  be  born  zvith  some  slight 
variation  profitable  to  some  part  of  its  economy/'^  Again 
Alphonse  de  Candolle^  speaking  of  acclimatization, 
says  in  a  similar  strain :  *'I1  f aut,  parait-il,  pour  une  modi- 
fication permettant  de  supporter  des  degres  plus  intenses 
de  froid,  des  periodes  beaucoup  plus  longues  que  4  ou 
5000  ans,  ou  des  changements  de  forme  et  de  duree."^ 
Of  more  modern  authors  J.  Costantin  writes  as  fol- 
lows:  ''Mais  si  pendant  50,  100,  1000  ans  Taction  du 
milieu  se  maintient  toujours  la  meme,  les  caracteres 
hereditaires  qui  evoluent  lentement,  se  consolident,  de- 
viennent  de  plus  en  plus  stables.'^ 

Numbers  of  similar  passages  will  doubtless  occur  to 
the  reader,  but  if  he  examines  them  carefully  he  will 
see  that  whilst,  to  Darwin,  the  long  period  of  time  meant 

^  Wallace,  Darwinism,  2d  ed.,  p.  89. 

'Life  and  Letters,  III,  p.  345. 

^  Ibid.,  II,  p.  124. 

*  Originc  des  plantes  cidtivees,  p.  371. 

'  Costantin,  Accomodation  des  plantes  aux  climafs  froid  et 
chaud.    Bull.  Scicntif.  de  Giard,  T.  31,  1897,  p.  489. 


Duration  of  the  Process  of  Selection.  87 

nothing  more  than  the  likelihood  of  the  chance  origin  of 
a  useful  change,  to  Wallace  on  the  other  hand  it  meant 
the  operation  of  time  by  the  gradual  cumulation  of  fluc- 
tuating variations  in  the  same  direction.  Other  authors 
sometimes  mean  one  of  these  things,  sometimes  the  other. 

The  ideas  involved  in  the  two  cases  are  of  course 
fundamentally  different.  Darwin's  view,  although  he 
never  definitely  formulated  it,  was  that  it  was  these 
occasional  single  variations  which  brought  about  the  con- 
tinual differentiation  of  living  forms.  In  short,  the  es- 
sential process  in  the  production  of  new  forms  is  the 
gradual  accumulation  by  natural  selection  of  these  small 
changes,  provided  they  are  useful.^ 

Wallace's  view  is  that  the  material  for  species- 
forming  selection  is  furnished  by  fluctuating  variability; 
and  that  these  infinitesimal  differences  are  gradually 
heaped  up  in  the  same  direction  until  ultimately  they 
attain  the  dimensions  of  specific  differences. 

Even  when  proof  can  be  brought  forward,  as  it  can 
in  the  case  of  many  cultivated  species,  that  plants  are 
different  from  what  they  were  one  or  two  thousand  years 
ago,  it  can  scarcely  ever  be  determined  historically  whether 
they  favor  the  former  or  the  latter  of  these  two  views. 
Those  cases  in  which  the  sudden  origin  of  a  new  form 
was  observed  and  described  by  contemporaries,  are  the 
exceptions :  and  they  tell  in  favor  of  Darwin's  view, 
and  never  in  favor  of  Wallace's. 

And  if  it  is  impossible  to  discriminate  between  the  two 
historically,  how  much  less  is  there  any  hope  of  a  verdict 
by  the  method  of  analogy,  when  there  are  no  definite  facts 
to  go  upon. 

This  being  the  case,  we  pass  on  to  the  consideration 

^  Life  and  Letters,  II,  p.  125. 


88      Selection  Does  Xot  Lead  to  Origin  of  Species. 

of  the  second  part  of  our  question :  what  may  be  expected 
in  the  future  as  the  result  of  continued  selection. 

It  is  generally  assumed  that  individual  variability  is 
unlimited,  moreover  that  as  a  result  of  continued  selec- 
tion in  any  direction  variation  continues  to  extend  in  the 
same  direction.  But  this  assumption  is  based  on  no  em- 
pirical foundation  whatsoever.  The  experiments  of 
breeders,  particularly  those  on  acclimatization  tell  in 
favor  of  strictly  limited  (although  agriculturally  highly 
important)  changes  only.-^  The  one  thing  about  which 
there  is  absolutely  no  doubt  whatsoever  in  this  question, 
is  the  fact  of  regression :  the  definite  backsliding  of  the 
mean  of  the  race  as  compared  with  the  extreme  indi- 
viduals chosen  as  seed-bearers. 

By  improved  methods  the  selection  process  can  be 
considerably  accelerated,  and  the  goal  reached  some  years 
earlier.  In  practice  important  results  have  been  obtained 
in  this  way,  but  tliey  are  not  of  such  a  kind  as  to  be  any 
help  in  this  discussion. 

I  have  already  had  occasion  to  remark  once  or  twice 
that  our  knowledge  of  regression  is  very  scanty,  con- 
sidering the  great  importance  of  the  phenomenon :  and 
that  much  remains  to  be  found  out  about  it.  If  it  should 
turn  out  that  as  a  result  of  continued  selection  the  yearly 
reversion  became  gradually  smaller  we  should  have  a  re- 
sult of  extraordinary  importance  for  the  theory  of  selec- 
tion. If  the  contrary  happened,  this  theory  would  have 
to  be  definitely  abandoned.  And  so  long  as  a  decision 
is  wanting,  the  theory  evidently  lacks  the  necessary  foun- 
dation. 

The  data  that  I  have  been  able  to  collect  tell  in  favor 
of  the  view  that  the  maximum  change  which  can  be 

*  Cf.  the  following  sections. 


Duration  of  the  Process  of  Selection.  89 

effected,  is  attained  as  a  rule  after  2  or  3  generations  or 
sometimes  after  4  or  5  or  perhaps  a  few  more.  We  are 
of  course  speaking  of  the  improvement  of  a  single  char- 
acter. In  practice  where  one  is  concerned  with  several 
or  more  characters  the  process  of  selection  may  of  course 
last  much  longer.  And  this  is  true  even  when  improved 
methods  render  possible  a  more  rigid  selection  from  vast 
numbers  of  individuals,  as  in  the  case  of  beet  culture 
where  however  one  is  usually  dealing  with  fractional 
percentages. 

In  scientific  experiments,  with  a  single  character  in 
view,  the  duration  of  the  period  of  selection  is  in  my 
opinion  to  be  placed  as  a  rule  at  from  2  to  4  generations.^ 
There  is  no  point  in  continuing  the  experiment  further 
unless  one  wishes  to  arrive  at  some  decision  on  the  ques- 
tion of  regression  which  we  have  just  been  discussing.^ 

I  am  convinced  that  great  harm  has  been  done  by 
this  exaggeration  of  the  length  of  the  process,  since  it 
must  have  deterred  many  investigators  from  instituting 
experiments  of  this  kind. 

I  shall  now  briefly  recapitulate  some  such  experi- 
ments gathered  from  the  early  literature  on  this  subject. 
The  first  I  refer  to  is  the  well-known  essay  of  P.  P.  A. 
Leveoue  de  Vilmorin  on  the  culture  of  the  wild  carrot 
{Dmicus  Carota).^  He  succeeded  in  less  than  5  genera- 
tions in  improving  the  wild  form  until  the  roots  were 

'  Cf.  Fritz  Muller's  breeding  experiment  with  maize :  Kosmos, 
loc.  cit. 

~  A  well-known  practical  difficulty  is  presented  by  the  fact  that 
it  is  only  after  cultivating  a  plant,  which  is  new  to  one,  for  a  con- 
siderable number  of  generations,  that  one  gets  to  know  its  needs  in 
the  matter  of  cultivation,  manure,  artificial  fertilization,  selection,  etc. 

^L.  De  Vilmorin,  Notices  sur  I'amcUoration  des  pJantcs  par  le 
semis,  i886;  cf.  pp.  10-12.  Also  Carriere,  Gardeners  Chronicle,  1865, 
P-  1 1 54- 


90      Selection  Does  Not  Lead  to  Origin  of  Species. 

fleshy  and  they  were  as  good  vegetables  as  the  ordinary 
cultivated  carrot.  In  the  same  way  Carriere  developed 
in  five  years  from  the  wild  radish  possessing  small  in- 
edible roots  a  vegetable  weighing  from  3  to  6  hundred 
grams. ^  Again  Buckmann  found  that  the  roots  of  the 
wild  parsnip  could  be  quickly  increased  in  size  by  selec- 
tion.^ 

We  may  conclude  therefore  that  it  does  not  take 
more  than  a  few  years  to  reach  that  point  which  remains 
constant  in  cultivation  if  selection  is  not  slackened.^ 

At  the  beginning  of  this  section  we  noted  as  the 
second  principle  of  selection,  the  belief  that  the  result 
of  selection  can  persist  independently  of  selection. 

Now,  it  is  manifest  that  specific  characters  are  abso- 
lutely independent  of  selection.  I  am  referring  of  course 
to  the  mean  characters  of  elementary  species,  for  the 
deviations  from  the  mean  are  themselves  the  material  for 
selection.  Over  200  species  of  Draba  verna  are  known ; 
these  come  true  to  seed  and  persist  as  such  independently 
of  selection  even  when  they  are  cultivated  side  by  side 
in  the  same  garden.  This  is  also  true  of  very  many 
"species."  Bateson  has  rendered  good  service  in  his 
great  book  Materials  for  the  Study  of  Variation  by  hav- 
ing directed  the  searchlight  of  criticism  on  these  weak 
points  in  the  theory  of  selection.  He  challenges  this 
theory  to  explain  how  the  undeniable  discontinuity  in  the 
series  of  species  can  have  arisen  from  the  continuity  of 
ordinary  variation.  No  such  explanation  has  been  of- 
fered.    For  artificial  selection  does  not  lead  to  the  origin 

*  J.  CosTANTiN,  in  Bull.  Scientif.  de  Giard,  1897,  p.  499.  Com- 
pare also  LiNDLEY,  TJicoyy  of  Horticulture,  p.  313. 

"  Darwin^  Das  Variiren  der  Pflanzen  und  TJiierc,  1,  p.  408. 

^  If  the  selection  stops  the  plants  revert  to  the  wild  form,  and 
this  also  in  a  short  time. 


Duration  of  the  Process  of  Selection.  91 

of  independent  types.  "Every  race  of  plants  possesses 
only  a  low  degree  of  constancy,"  says  one  of  our  most 
considerable  agricultural  authorities,  Prof.  Kurt  von 
RuMKER.^  Without  a  continuation  of  selection  they 
would  soon  lose  their  good  qualities.  In  this  respect 
they  behave  quite  differently  from  a  true  species  or  con- 
stant variety. 

There  is  no  need  for  me  to  go  further  into  this  matter 
now,  for  I  shall  make  it  my  business  in  the  following 
paragraphs  to  point  out  what  the  experience  of  breeders 
can  teach  us  on  this  point. 

Finally  I  should  like  to  discuss  a  very  instructive 
example  more  thoroughly.  I  refer  to  the  important  ob- 
servations of  R.  VON  Wettstein  on  seasonal  dimor])hism 
as  a  point  of  departure  for  the  origin  of  species  in  the 
vegetable  kingdom.^  He  deals  with  the  genera  Gentiana, 
Euphrasia,  Alectorolophus  (Rhinanthus).  In  the  alpine 
meadows  there  occur  in  the  case  of  many  species  of  these 
genera  two  forms  (varieties,  subspecies,  or  elementary 
species)  of  which  one  flowers  early  and  the  other  late. 
Moreover  the  early  and  late  flowering  forms  of  one  pair 
are  usually  distinguished  from  one  another  by  a  series 
of  further  characters  of  the  value  of  the  differences  be- 
tween elementary  species. 

The  time  for  mowing  the  grass  in  Central  Europe 
falls  between  the  flowering  season  of  these  two  varieties. 
The  early  kinds  ripen  their  seeds  before  this  time ;  the 
later  only  begin  their  main  growth  after  it. 

The  work  of  von  Wettstein  clearly  shows  that 
these  species  are  associated  in  pairs  and  has  proved  that 

^  Der  wirthschaftliche  Mehrwertli  guter  Culfiirvanetdten,  1898, 
p.  136  of  the  offprint. 

^  Bcrichte  d.  d.  hot.  Gesellsch.,  1895,  Bd.  XIII,  p.  303,  and  Bot. 
C entralblatt ,  1900,  No.  i,  p.  15. 


92      Selection  Docs  Not  Lead  to  Origin  of  Species. 

their  separation  was  brought  about  by  selection  in  the 
field.  But  that  obviously  does  not  settle  the  question 
as  to  whether  these  pairs  have  arisen  by  a  process  of 
gradual  change  or  of  sudden  convulsion.  These  most 
important  results  considered  in  relation  to  the  subject 
under  discussion  not  only  do  not  enable  us  to  decide,  for 
this  particular  case,  between  the  mutation  and  the  selec- 
tion theory,  but  they  also  leave  undecided  the  question 
whether  (supposing  the  latter  is  true)  the  change  was 
completed  in  a  few  generations,  or  was  attained  in  the 
course  of  centuries. 

§  10.   ACCLIMATIZATION. 

Acclimatization  is  perhaps  the  best  touchstone  that 
can  be  used  for  testing  the  efficacy  of  the  doctrine  of 
selection.  Selective  breeding,  which  so  often  has  to 
overcome  natural  selection,  in  this  case  works  in  accord 
with  it.  Moreover  there  is  a  strong  agreement  between 
artificial  and  natural  acclimatization,  whether  this  latter 
be  the  result  of  migrations  of  organisms  or  of  essential 
changes  in  their  climatic  or  cecological  environment. 

It  is  here  therefore  that  we  have  most  chance  of  find- 
ing out  how  much  natural  selection  is  capable  of  doing. 

But  the  harvest  turns  out  ver}'  scanty — so  scanty  in- 
deed that  the  upholders  of  the  doctrine  of  selection  are 
loath  to  assign  it  a  very  prominent  position  among  their 
arguments. 

In  practice  the  process  of  acclimatization  is  extra- 
ordinarily complex.  In  most  cases  we  are  only  concerned 
with  finding  out  whether  such  and  such  a  species  can 
grow  in  a  new  locality  or  not.  And  we  find  that  either 
the  difference  between  the  old  and  the  new  localitv  has 


Accliinatization.  93 

no  effect  or  that  partial  adaptations  appear,  of  the  kind 
with  which  we  are  acquainted  through  Bonnier's  ex- 
periments with  alpine  plants.-^  It  may  also  happen  that 
the  species  in  its  old  locality  consists  of  a  group  of  sub- 
species of  which  some  are  suited  to  the  new  climate  while 
some  are  not;  in  such  a  case  all  that  remains  to  be  done 
is  to  find  out  which  are  suited  and  which  not. 

On  the  theoretical  side  we  may  apply  the  theory  of 
acclimatization  to  the  solution  of  the  problem  of  the 
distribution  of  a  single  species  over  vast  regions,  as  for 
example  in  the  case  of  maize  in  America.  The  climate 
of  a  locality  determines  the  subspecies  which  inhabit  it, 
sometimes  favoring  a  tall  luxuriant  plant  laden  with 
large  ears  heavy  with  seed,  som.etimes  small  plants  ripen- 
ing in  a  few  weeks  wnth  little  ears  and  seeds  (Fig.  20). 

But  whether  such  subspecies  have  arisen  by  gradual 
selection  or  by  mutations  can  of  course  no  longer  be  de- 
termined empirically. 

The  process,  however,  which  is  really  interesting  to 
us  here,  is  the  conscious  or  unconscious  selection  of  in- 
dividuals which  are  best  adapted  to  the  new  conditions : 
in  other  words  the  establishment  of  a  new  race  bv  means 
of  the  material  supplied  by  fluctuating  variation. 

Before  passing  on  to  consider  this  case  in  detail  I 
should  like  to  mention  an  example  which  more  than  any 
other  shows  how  careful  we  must  be  in  using  practical 
experience  for  the  solution  of  scientific  problems.  It  is 
the  case  of  a  result  obtained  by  one  of  the  most  distin- 
guished growers  in  Germany,  J.  IMetzger,  and  of  its 
scientific  application  by  Darwin  himself,  It  is  the  case — 
so  well  known  and  so  often  quoted — of  the  transforma- 
tion of  an  American  variety  of  maize  into  the  ordinary 

Compare  also  §  17,  pp.  144-146. 


94      Selection  Does  Not  Lead  to  Origin  of  Species. 


maize  of  Baden,  within  three  years  after  its  introduction 
into  Germany. 

Darwin  quotes  Metzger^s  Getreidearten,  translating 
word  for  word.    Metzger's  Landwirthschaftliche  P flan- 


Fig.  20.  Ears  of  Maize  of  Commerce.  All  the  fig- 
ures reduced  on  the  same  scale  (Vs).  i.  Giant 
yellow  Dent  field  corn.  2.  Miniature  maize  (Zea 
gracillima).      3.    Pop-corn    (white    Rice    Maize). 

senkunde  lies  before  me;  it  contains  the  description  of 
the  observation  on  page  208  in  the  first  volume.-^  Dar- 
win calls  this  case  the  most  remarkable  instance  knozvn 

^  Darwin,  Variations  of  Animals  and  Plants  Under  Domesti- 
cation. I,  p.  340.  Metzger,  Getreidearten,  p.  208,  Landivirthsehaft- 
liche  Pflanzenkunde  ( ?  the  same  work)  1841,  I,  p.  208.  Cf.  also 
Wallace,  Darwinism,  2d.  ed.,  p.  419. 


Acclimatization.  95 

to  me  of  the  direct  and  prompt  action  of  climate  on  a 
plant,  and  Wallace  regards  this  transformation  as  a 
result  of  that  "reversion  to  mediocrity'  which  invariably 
occurs  and  is  more  especially  marked  in  the  case  of  vari- 
eties zvhich  have  been  rapidly  produced  by  artificial  se- 
lection. It  may  be  considered  as  a  partial  reversion  to  the 
wild  or  unimproved  stock. 

Let  us  now  see  what  Metzger  says.  He  is  deaHng 
with  a  white  broad-seeded  American  Maize,  the  Taras- 
cora  Corn  from  St.  Louis. 

''We  cultivated  this  form^  and  got  stems  12  feet 
high  in  the  first  years  and  only  a  few  ripe  seeds  of  which 
the  lowest  on  the  cob  were  like  the  original  form  whilst 
the  upper  ones  appeared  to  lack  the  depressions  and  to 
show  features  like  those  of  the  European  Maize. 

"We  sowed  the  seeds  from  these  next  year  and  ob- 
tained plants  from  9  to  10  feet -high  whose  seeds  ripened 
earlier.  The  seeds  were  noticeably  larger  than  in  the 
previous  year,  the  depression  on  the  surface  had  already 
disappeared  and  the  beautiful  white  color  appeared  darker 
and  dirtier.  Some  seeds  were  yellow;  and  their  round 
form  was  just  like  that  of  our  own  maize  and  betrayed 
no  signs  whatever  of  the  characters  of  the  form  from 
which  they  had  sprung.  In  the  third  year  of  the  culti- 
vation all  the  characters  of  the  American  form  had  dis- 
appeared and  the  American  maize  had  been  transformed 
into  subspecies  5  form  B.^  We  obtained  another  lot 
of  the  seed  of  this  same  varietv  which  in  the  third  vear 
approached  the  same  subspecies  5,  B  and  exactly  resem- 
bled it  after  six  years  of  cultivation.     This  maize  is  now 

^  From  the  description  the  variety  must  have  belonged  to  the 
Dent  corns.  ^ 

^  Large  White  European  Maize.     Zca  praecox  L.,  p.  213. 


96      Selection  Does  Not  Lead  to  Origin  of  Species. 

often  grown  in  our  neighborhood  and  can  be  distin- 
guished from  our  common  form  only  by  its  somewhat 
more  ''branching  habit." 

I  can  find  nothing — not  even  a  suggestion — in  Metz- 
ger's  account  about  the  cause  of  this  transformation. 
But  any  one  having  an  acquaintance  with  hybridization 
and  the  so-called  running  out  of  cereals  will  see  that  Metz- 
GER^s  case  is  not  an  instance  of  the  transformation  of  a 
race  by  climatic  influences.  The  cultures  of  the  Taras- 
cora  maize  stood  between  other  kinds  and  were  obviously 
liable  to  be  fertilized  by  the  pollen  of  these  through  the 
agency  of  the  wind.  Some  of  the  seeds  would  in  that 
case  give  hybrids  which  could  give  rise  in  the  third  gen- 
eration to  pure  European  maize. -^ 

The  hybrids  and  their  pure  European  progeny  would 
be  likely  to  supplant  the  foreign  strain  which  would  be 
less  adapted  to  the  climate  of  Baden;  and  this  would  take 
place  in  a  much  shorter  time  than  one  would  be  inclined 
to  think.  And  inasmuch  as  this  supplanting  of  one  sort 
by  another  has  been  so  often  mistaken  for  the  supposed 
transformation  of  a  species  or  even  for  the  creation  of 
a  new  one  it  is  worth  while  to  cite  in  some  detail  a  few 
examples  which  may  be  selected  from  Rimpau's  cele- 
brated w^ork :  Rislers  Wcizenhaii.  The  first  example  is 
an  observation  of  Risler;-  the  second  is  due  to  Rim- 
PAU  himself. 

RiSLER  describes  a  case  of  degeneration  of  GaUand 
wheat  during  the  first  few  years  after  its  introduction 
into  his  estate  at  Caleves  on  Lake  Geneva  in  Switzer- 
land.    The  ears  of  this  variety,  when  they  make  their 

^A  more  exact  discussion  of  this  point  will  be  given  elsewhere. 

^EuG.  RiSLER,  Der  Weisenbau.  Translated  by  W.  Rimpau; 
Thaer-Bibhothek,  P.  Parey,  1888,  pp.  73-74. 


i 


Acclimatization. 


97 


first  appearance,  have  beards;  but  lose  them  when  thev 
ripen.  In  the  first  year  in  the  new  environment  prac- 
tically all  the  ears  with  very  few  exceptions  had  this 
character;  but  in  the  second  year  already  half  were  beard- 
less, whilst  in  the  third  year  the  latter  formed  the  great 


Fig.  21.     Rough  Awned  Wheat  of  Rivett  and  ordi- 
nary German  Field  Wheat. 

majority;  they  also  differed  from  the  original  form  in 
the  fact  that  their  seeds  had  a  horny  instead  of  a  mealy 
texture. 

To  determine  the  cause  of  this  degeneration  Risler 


\ 


98      Selection  Does  Not  Lead  to  Origin  of  Species. 

sowed  alternating  rows  of  Galland  wheat  and  beardless 
wheat;  and  it  was  discovered  that  the  former  suffered 
more  from  the  cold  of  winter  than  the  latter  and  that  it 
ripened  from  8-14  days  later;  these  two  differentiating 
characters  sufficed  to  enable  the  small  initial  admixtures 
of  the  beardless  wheat  to  get  the  upper  hand  within  three 
years. 

RiMPAU^s  observation  concerns  the  rough  wheat  (Ri- 
vett's  Bearded,  Fig.  21)  of  which  it  is  often  asserted 
that  it  easily  degenerates  and  that  after  a  few  years  it 
always  contains  a  larger  or  smaller  proportion  of  beard- 
less examples.  But  when  kept  absolutely  free  from  ad- 
mixture, as  in  RiMPAu's  experiments  in  Saxony,  this 
form  remains  perfectly  true;  as  indeed  it  has  done  in 
Scotland  for  over  a  hundred  years.  "But  it  was  more 
liable  than  any  of  the  varieties  of  wheat  we  grow  to  suffer 
from  the  winter,  and  as  it  develops  later  in  the  spring 
than  all  other  sorts  it  is  easy  to  understand  that  all  chance 
admixtures,  which  are  unavoidable  in  cultivation  on  a 
large  scale — and  are  apt  to  be  introduced  by  the  use  of 
farmyard  manure — will  multiply  much  more  rapidly  and 
soon  obtain  the  upper  hand."-^ 

The  results  of  experiments  in  acclimatization,  there- 
fore, can  only  be  used  as  scientific  evidence  when  the 
danger  of  crosses,  or  of  degeneration  by  the  chance  ad- 
mixture of  native  races  is  absolutely  excluded. 

The  best  examples  have  been  collected  by  Schubeler 
who  is  himself  responsible  for  some  of  the  results  in  his 
collection.-     They  relate  chiefly  to  the  acclimatization  of 

*  It  is  well  known  that  in  bad  years  Avena  fatua  multiplies  rap- 
idly among  oats ;  it  contributes  nothing  to  the  yield.  Godron,  De 
I'Espece,  I,  p.  163. 

^  Schubeler,  Die  Pilan::enwelt  Norzvegens,  1875.  Also,  Die 
Culturpiianzen  Norwegens. 


i 


Sugar  Beets.  99 

maize  and  other  cereals  to  northern  locaHties  and  to 
mountain  districts,  in  other  words  to  the  extension  of 
the  cuhure  of  cereals  into  higher  altitudes  and  latitudes. 
This  end  is  usually  attained  by  shortening  the  period  of 
growth  and  by  being  content  with  a  correspondingly 
smaller  harvest.  In  the  case  of  chicken-maize,  for  ex- 
ample, the  duration  of  life  was  shortened  from  four  to 
three  months  in  the  course  of  five  years.  The  same 
happened  in  the  case  of  rye  and  wheat.  During  the  first 
few  years  of  the  culture  it  is  only  the  individuals  that 
flower  first  that  ripen  their  seeds,  and  this  of  itself  brings 
about  an  effective  process  of  selection.  In  the  same  way, 
though  in  this  case  deliberately,  the  flowering  time  of 
Chrysanthemum  indicnm  has  been  partly  shifted  back 
to  July  and  partly  advanced  into  the  following  February. 
The  same  is  true  of  innumerable  garden  plants,  of  various 
varieties  of  cucumbers,  and  so  on. 

But  the  available  experience  on  acclimatization  does 
not  go  much  further  than  this;^  and  we  ma}^  be  quite 
sure  that  new  specific  characters  have  never  arisen  in  this 
way. 

§   II.    SUGAR   BEETS. 

Sugar  beets  afford  the  finest  example  of  the  process 
of  artificial  selection.  In  no  other  plant  under  culti- 
vation has  the  technique  of  selection  reached  so  high  a 
pitch  of  perfection ;  in  no  other  is  the  method  so  sure 
or  the  result  so  certain.  There  is  now  no  sale  for  beet 
seed  which  has  not  been  the  result  of  careful  selection. 

Experiments  in  the  selection  of  sugar  capacity  began 
about  1850.     This  instance  shows  best,  therefore,  what 

^  A  review  of  the  subject  is  given  in  J.  Costantin's  splendid 
work:  Accomodation  dcs  planfcs  aux  climats  froid  ct  chaud.  Bull. 
Scientif.  de  Giard^  XXXI,  1897,  p.  489. 


100    Selection  Does  not  Lead  to  Origin  of  Species. 

can  be  achieved  within  half  a  century  by  continued  selec- 
tion in  one  and  the  same  direction,  hand  in  hand  with 
continual  improvement  of  method. 

Progress  has  been  enormous :  the  average  content 
of  the  common  beet,  which  at  first  was  a  matter  of 
7-8%,  is  now  double  that  amount.  Shape,  size,  and 
w^eight,  the  character  of  the  leaves  and  especially  the 
reduction  in  woody  tissues  have  all  been  the  object  of 
selection,  and  have  made  the  beet  much  more  valuable 
from  the  industrial  point  of  view. 

All  this  has  been  done  by  selection  of  the  best  indi- 
viduals afforded  by  ordinary  fluctuating  variation.  Nei- 
ther spontaneous  variations  nor  crossings  have  played 
any  part  in  it.  We  are  dealing  here  with  the  process  in 
its  simplest  form. 

This  is  not  the  place  to  praise  the  genius  of  Louis 
ViLMORiN^  the  founder  of  the  method,  or  the  achieve- 
ments of  his  numerous  successors  especially  in  Germany. 
Nor  need  I  describe  the  marvelous  technical  process  by 
which  it  is  possible  to  determine  the  polarization  indices 
of  more  than  100,000  beets  in  a  few  weeks.  ^ 

On  the  contrary  I  am  only  concerned  with  showing 
how^  little  value  these  splendid  results  have  in  the  discussion 
of  the  process  of  the  origin  of  species.  On  the  botanical 
side  no  better  argument  for  the  theory  of  selection  could 
be  adduced.  Yet  in  this  case  there  is  nothing  which  is 
in  the  remotest  degree  like  the  origin  of  a  new^  species 
nor  even  anything  that  could  lead  us  to  expect  that  any 
form  of  the  systematic  value  of  a  species  could  arise  in 
this  wav. 

^  I  particularaly  recommend  to  the  scientific  reader  the  study  of 
Prof.  Kurt  von  Rumker's  short  and  clear  paper:  Die  Zuckerriiben- 
zdichiung  dcr  Gegenwart.  (Blatter  fiir  Zuckerriibenbau,  1894,  PP- 
1-48.) 


Sugar  Beets.  101 

Of  course  I  am  not  speaking  of  the  origin  of  the 
sugarbeet  itself.  We  know  as  Httle  of  its  origin  as  we  do 
of  the  origin  of  the  other  varieties  of  beets.  The  Romans 
probably  had  only  two  sorts  which  they  used  as  vege- 
tables, which  they  cultivated  in  their  gardens  and  col- 
lected in  the  wild  state. ^  At  the  beginning  of  the  nine- 
teenth century  there  were  numerous  kinds.  The  ques- 
tion arises :  did  they  originate  from  the  older  forms  in 
culture,  or  were  they  first  found  as  distinct  subspecies 
in  nature  ?  We  do  not  know.  That  they  had  a  common 
origin  we  do  not  doubt,  but  whether  they  originated  be- 
fore or  during  cultivation  remains  a  mystery. 

The  beet  with  which  Vilmorin  began  his  work  half 
a  century  ago  must  be  regarded  simply  as  a  starting 
point;  artificial  selection  is  responsible  only  for  what  it 
has  given  rise  to. 

As  far  back  as  1830-1840  Vilmorin  had  selected 
his  beets  according  to  their  external  form.  In  1851  he 
determined  the  saccharine  contents  of  single  roots  and 
found  that  it  varied  from  7-14%,  but  the  troublesome 
nature  of  the  methods  of  estimation  available  at  that 
time  only  permitted  of  the  determination  of  compara- 
tively few  instances.  He  discovered  the  best  beets  by 
their  high  specific  gravity  in  salt  solutions,  sowed  the 
seeds  which  they  produced  and  got  beets  with  21%  sugar 
in  the  second  generation.^ 

These  figures  (7-14-21%)  are  very  important  in  this 
connection.  It  must  be  remembered  of  course  that  they 
cannot  be  compared  very  exactly  with  the  results  of 
recent  work  because  the  method  has  become  much  more 

^  Plinius,  N.  H.  Lib.  19.  See  also  Columella  and  Cicero 
(Note  of  1908). 

^L.  LEyEQUE  DE  Vilmorin,  Notices  snr  I'auiclioration  dcs  f^lantes 
par  le  semis.    2d  edition,  1886;  see  especially  p.  2y. 


102    Selection  Does  Not  Lead  to  Origin  of  Species. 

simple  and  precise,  especially  since  the  introduction  of 
the  use  of  the  polariscope. 

But  it  is  more  likely  that  Vilmorin's  figures  were 
too  low  than  that  they  were  too  high. 

1874  was  the  first  year  in  which  the  method  of  polari- 
zation was  employed  and  the  selection  based  on  the  re- 
sults of  this  method.  The  normal  contents  ranged  at  that 
time  between  10-14%.  In  bad  years  with  a  mean  of 
10%  ;  in  good  ones  it  was  from  12  to  14%.^  Even  cases 
of  9.5  and  17.5%  were  not  rare.^  From  1878  to  1881 
the  method  of  polarization  spread  in  Germany  and  Aus- 
tria; I  need  only  mention  the  names  of  Dippe  of  Qued- 
linburg,  Rimpau^  Heine  and  the  Klein-Wanzleben  fac- 
tory. The  progress  was  slow  but  sure.  In  most  factories 
the  beets  are  examined  only  comparatively,  except  in 
the  case  of  the  best  ones,  in  which  the  polarization  index 
w^as  actually  determined.  In  the  w^orks  of  Messrs. 
KuHN  &  Co.,  however,  at  Naarden  (Holland)  this  in- 
dex has  been  directly  determined  every  year  for  over 
300,000  plants.  Through  the  kindness  of  these  gentle- 
men I  obtained  in  1896  the  indices  of  40,000  roots;  they 
made  a  very  beautiful  curve  with  a  mean  at  15.5%  (Fig. 
22.) 

Selection  is  then  carried  out  with  reference  to  these 
figures  in  such  a  way  that  sufficient  plants  are  always 
available  for  seed.  The  result  of  polarization  deter- 
mines the  limits  of  the  groups.  I  shall  now  give  some 
figures  for  1892.  Roots  with  less  than  14%  were  not 
planted  for  seed.  Those  with  from  14-16%  formed  the 
seed  plants  for  commercial  seed ;  there  were  20  to  30  of 

^  Langethal,  LandwirthschaftUche  PHanzcnkimde,  III,  1874,  P- 
69. 

^  Jahreshericht  dcr  Zuckerindustrie,  Vol.  9,  p.  39  etc. 


Sugar  Beets. 


103 


these  in  every  100  plants  examined.  Those  with  from 
16-18%  became  the  seed  plants  for  the  special  race,  the 
so-called  elite  race  from  whose  seeds  the  beets  were 
produced  which  would  be  tested  in  the  next  generation. 
In  1892  there  were  among  180,000  polarizations  only 
four  instances  of  a  higher  percentage  than  18%  in  the 


lis   n    izs  13    13.S  rt    ;w    is    iss   i6    res   n    ns  ia    las  19 
Fig.  22.  Variation  in  the  Amount  of  Sugar  in  40,000  Beets.^ 


above  mentioned  factory.  Since  that  time  the  annual 
number  of  polarizations  as  already  mentioned  has  reached 
about     300,000;     and     the    maximum    percentage     has 

^  The  polari^^ations  in  question  were  carried  out  from  January 
23  to  February  5  in  1896  and  gave  the  following  figures: 

Sugar  %   .    .  . .     12       12.5        13       13.5        14       14. 5        15       15.5 
.    340      635      1 192    2205     3597    5561     7178    7829 

.     16       16.5        17       17.5        18       18.5        19 
.  6925     4458    2233     692       133        14         5 

Individuals  with  less  than  12%  have  been  excluded  from  this  series. 
The  dotted  line  is  the  theoretical  curve  according  to  Quetelet's 
law,  {a-^-hy^ ;  the  discrepancy  between  it  and  the  actual  curve  on  the 
left  side  is  probably  due  to  the  presence  of  some  faulty  beets. 


Individuals 

Sugar   %   . 
Individuals 


104    Selection  Docs  Not  Lead  to  Origin  of  Species. 

mounted  to  21%,  and  the  other  figures  have  risen  cor- 
respondingly. Commercial  beet  grown  from  this  selected 
seed,  has  on  the  average  13  to  14%  sugar. 

Without  underrating  the  high  agricultural  signifi- 
cance of  these  results  we  must  nevertheless  face  the  fact 
that  there  is  very  little  in  them  which  can  serve  as  a 
basis  for  a  decision  of  the  question  of  the  origin  of 
specific  characters.  We  cannot  be  certain  whether  after 
selection  for  fifty  years,  i.  e.,  for  25  generations,  the 
upper  limit  of  the  range  of  variability  has  been  essentially 
extended  or  not.  It  so  happens  that  this  limit — 21% — 
is  the  same  in  Vilmorin's  instance  (1853)  and  in  the 
works  at  Naarden  (1892-1898),  but  there  are  other 
races  under  different  conditions  of  cultivation,  whose 
limit  is  stated  to  be  as  high  as  26%.  The  wider  range 
of  modern  polarization  work  with  beets  evidently  gives 
a  chance  of  higher  percentages. 

The  average  product  of  a  field  has  certainly  Increased 
from  7-8%  to  14-16%  and  more.  But  this  improvement 
is  dependent  on  the  continuation  of  selection;  and  it  is 
only  by  this  means  that  it  has  reached  this  pitch.  Every 
sugar  manufacturer  knows  that  selection  is  an  indis- 
pensable condition  of  a  satisfactory  harvest.  It  is  true 
that,  for  the  purpose  of  obtaining  the  necessary  quantity 
of  seed,  a  so-called  intermediate  generation  is  inter- 
])olated  between  polarization  and  seed-harvest:  but  if 
more  than  one  or  at  most  two  (and  this  happens  very 
seldom)  of  these  are  introduced  the  advantage  gained 
by  polarization  and  selection  is  lost.  By  no  manner  of 
means  is  the  improvement  independent  of  selection;  on 
the  contrary  the  promise  of  more  sugar  can  only  be 
fulfilled  by  a  further  perfection  of  the  method  of  polari- 
zation and  by  continued  efforts  on  the  part  of  breeders. 


Sugar  Beets.  105 

Since  the  method  of  polarization  was  introduced  the 
progress  of  the  sugar  beet  has  been  slow  but  continuous. 
But  it  must  not  be  concluded  from  this  that  the  present 
maximum  could  not  have  been  reached  in  a  few  genera- 
tions. At  any  rate  we  are  not  justified  in  deriving  this 
conclusion  from  the  evidence  at  hand.  Progress  has 
obviously  been  due  to  the  steady  improvement  in  meth- 
ods of  selection.  This  has  consisted  first  in  the  inven- 
tion of  the  boring  cylinder  which  enables  us  to  polarize 
directly  the  beets  to  be  selected;  Vilmorin  and  his  im- 
mediate followers  had  to  sacrifice  the  whole  beet  to  their 
chemical  analysis,  and  then  to  select  others,  resembling 
the  best  ones  in  specific  gravity,  for  cultivation.  And 
secondly  by  employing  larger  and  larger  groups  to 
choose  from,  (in  the  best  factories  every  year  more  than 
100,000  beets).  For  it  is  evident  that  the  larger  number 
there  is  to  choose  from,  the  greater  chance  is  there  of 
finding  desirable  ones. 

Beets  have  been  selected  not  merely  with  regard  to 
their  saccharine  contents  but  also  with  regard  to  their 
external  features.  This  takes  place  in  the  field  at  the 
time  of  harvest,  that  is  to  say,  before  polarization.  In 
most  factories  about  %o  are  thrown  away  in  this  process 
and  onl}^  %o  saved.  Breeders  are  of  the  opinion  that  on 
the  whole  this  %o  includes  plants  inferior  in  respect  to 
their  saccharine  contents  and  that  by  this  selection  a 
beneficial  effect  on  the  percentage  of  sugar  itself  is 
brought  about. -^  In  this  preliminary  selection  attention 
is  paid  first  to  the  leaves;  the  features  dealt  with  being 
their  shape,  their  size  and  the  angle  which  they  make 
with  the  zenith,  as  well  as  the  general  features  which 
control  assimilation,  transpiration  and  the  non-retention 

*v.  RiJMKER,  Zuckerrilhensuchtung,  p.  5. 


106    Selection  Does  Not  Lead  to  Origin  of  Species. 

of  rain  water.  The  various  kinds  of  beet,  in  which  selec- 
tion has  had  different  objects  in  view,  can  be  recognized 
by  their  foHage  in  the  field.  The  form  of  the  root  is 
very  important ;  it  should  be  unbranched ;  the  more  like 
the  roots  are  to  one  another  the  more  easily  can  they  be 
dealt  with.  The  dimensions  of  the  stem,  or  the  head 
as  it  is  called,  and  many  other  points  have  all  to  be  con- 
sidered and  especially  the  size  or  the  weight,  of  the 
whole  beet. 

Individual  breeders  pay  attention  to  trivial  charac- 
ters as  for  example  the  red  color  in  the  seedling  with 
the  object  of  facilitating  the  detection  of  impurities  in 
their  strains  in  the  field. 

It  is  absolutely  essential  to  keep  one's  eye  on  all  these 
points  in  every  generation.  In  the  case  of  no  single 
character  can  selection  be  relaxed.  Any  disregard  of 
these  rules  on  the  part  of  the  breeder  would  soon  lead 
to  a  degeneration  of  the  whole  race. 

*'Each  race  of  plant  possesses  only  a  very  small  de- 
gree of  constancy."  Herein  lies  the  difference  between 
the  improved  race  and  the  species.  This  already  quoted 
expression  of  Von  Rumker^  sums  up  clearly  and  con- 
cisely the  whole  significance  of  agricultural  results  in 
their  bearing;  on  Natural  Selection. 


'fe 


§  12.   CEREALS. 

Next  to  the  sugar  beet  the  cereals  have  furnished  the 
most  important  material  in  connection  with  scientific  and 
practical  experiments  in  selection,  though  in  the  latter 
case  the  general  conditions  are  much  less  simple. 

Modern   efforts  to   improve  the   races   had   to   start 

'Von   RiJMKER,  Der  LandwirthschaftUche  Mchrwerth,  loc.  cit 
p.  136. 


Cereals.  1 07 

with  a  vast  assemblage  of  varieties  of  unknown  origin. 
According  to  Nilsson,,  every  larger  or  smaller  "species" 
includes  hundreds  of  such  varieties.  In  the  second  place 
one  of  the  tasks  of  rational  breeding  is  to  cross  these 
sorts  with  one  another  as  much  as  possible  in  order  to 
combine  their  characters  in  the  particular  way  which 
seems  most  desirable  for  each  separate  case.  The  origin 
of  these  hybrids  is  in  most  cases  unknown,  or  at  best 
the  information  concerning  them  is  either  incomplete  or 
uncertain.  The  excellence  and  variety  of  our  cereals 
can  only  be  attributed  in  a  small  degree  to  the  direct 
effects  o*f  selection. 

In  his  excellent  treatise  Anlcitung  ::nr  Gctreidemich- 
tung  Von  Rumker  distinguishes  between  empirical  and 
methodical  selection.^  Empirical  selection  is  the  general 
process  which  every  intelligent  farmer  ought  to  prac- 
tise ;  it  is  carried  on  on  a  large  scale  in  certain  districts, 
as  for  example  the  Probstei,  where  the  entire  harvest  is 
sold  as  seed.  Empirical  selection  consists  at  least  in 
choosing  the  best  piece  of  the  field,  and  in  growing  the 
seed  for  the  next  year  on  it.  Or  the  harvest  is  threshed, 
the  largest  and  heaviest  grains  are  separated  from  tlie 
less  valuable  ones  by  a  hand  sieve  or  by  a  centrifugal 
machine,  and  kept  for  sowing.  Thirdly  a  sorting  by 
ears  is  carried  out  at  mowing  time  and  consists  in  set- 
ting aside  the  beast  ears  borne  by  the  strongest  halms  in 
sufficient  quantity  to  provide  for  the  elite  race  for  the 
ensuing  year. 

The  object  of  empirical  selection  is  to  keep  the  dif- 
ferent kinds  pure  and  to  put  a  stop  as  much  as  possible 

*Dr.  Kurt  von  Rumker,  Anleitiing  ziir  Getrcidczi'ichtung  auf 
ivissenschaftlicher  und  praktisclicr  Gnindlage,  Berlin,  1889.  Com- 
pare also  RisLER-RiMPAU,  Der  Weizenbau  in  the  Thacr-Bibliothek, 
1888. 


108    Selection  Does  Not  Lead  to  Origin  of  Species, 

to  the  degeneration  resulting  from  the  admixture  of  in- 
ferior varieties  (cf.  pp.  96-98).  Even  if  only  for  this  rea- 
son it  ought  never  to  be  slackened.  Then  again  it  is 
concerned  with  keeping  the  kinds  which  have  been  im- 
proved by  selection  up  to  the  mark;  without  it  they 
would  steadily  deteriorate  and  necessitate  the  purchase 
of  fresh  seed  too  often.  Lastly  it  adapts  varieties  to 
local  conditions  of  culture :  no  two  localities  are  alike 
with  regard  to  soil,  climate  and  manure. 

In  certain  districts  (Probstei,  Ostsee,  Hanna  and  the 
Tirol)  empirical  selection  has  been  practised  for  more 
than  a  century  on  a  large  scale  by  the  majority  of  the 
peasants  engaged  in  growing  cereals.  As  a  result  they 
sell  their  whole  crop  as  stock  seed  at  a  high  price.  But 
in  order  to  keep  up  the  good  reputation  of  their  varie- 
ties it  is  necessary  that  selection  should  continue  with- 
out ceasing.  It  is  very  difficult  to  tell  whether  this  form 
of  selection  leads  to  a  further  amelioration  of  these 
races  because  real  improvements  undoubtedly  are  made 
from  time  to  time  as  the  result  of  improved  methods  of 
selection.  But  the  essential  fact  is  that  no  race  which 
is  independent  of  selection  has  yet  arisen  in  this  way. 

Methodical  selection  is  based  on  an  entirely  different 
principle.  It  is  carried  on  by  a  few  men  at  the  head  of 
their  profession  and  its  object  is  to  put  new  and  valuable 
races  on  the  market.  Each  such  race  consists  of  two 
parts.  First  the  pedigree  or  the  so-called  elite  and  sec- 
ondly seed  for  the  market  and  for  the  trade. 

The  originator  of  a  race  of  this  kind  keeps  the  pedi- 
gree stock  on  his  own  property.  This  stock  does  not 
amount  to  more  than  a  few  or  at  any  rate  to  more  than 
a  few  hundred  individuals  in  a  year,  and  is  the  product 
of  the  selected  seeds  of  the  previous  generation.     Of  the 


Cereals.  1 09 

seeds  which  it  produces  only  the  very  best  are  kept  for 
sowing  for  the  continuation  of  the  stock.  The  com- 
mercial race  is  not  in  the  strict  sense  of  the  term  a  race, 
for  the  successive  generations  which  compose  it  are  not 
genetically  connected.  Each  generation  begins  as  a  lat- 
eral branch  of  the  main  stem;  the  first  harvest,  after  the 
seeds  for  the  pedigree  stock  have  been  set  apart  (and 
after  inferior  seeds  have  been  rejected)  is  grown  on 
special  fields  for  at  most  2  or  3  generations  to  produce 
the  quantity  of  seed  required  for  the  market.  In  every 
successive  year,  therefore,  the  stock  for  the  market  starts 
as  a  new  branch  of  the  main  stem ;  it  is  not  for  two  or 
three  years  after  improvements  appear  in  the  latter  that 
they  are  obtainable  in  the  former. 

It  obviously  follows  from  this  that  the  race  never 
becomes  independent  of  selection,  as  a  true  species  or 
subspecies  does.  There  are,  of  course,  beautiful  ex- 
amples of  subspecies  among  cereals,  but  they  have  not 
arisen  by  selection.  Patrick  Shirreff's  older  varieties 
are  examples  of  these;  they  are  independent  of  selection 
and  often  so  good  that  they  cannot  be  improved  by  it — 
e.  g.,  the  Talavcra  wheat.  A  sharp  distinction  must 
therefore  always  be  made  between  species  and  subspecies 
on  the  one  hand,  and  races  on  the  other. 

The  greater  the  improvement  of  a  race  has  been,  the 
more  does  it  deteriorate  in  ordinary  cultivation ;  its  seed 
can  only  quite  exceptionally  be  used  for  further  crops.  ^ 

IMethodical  selection  is  of  tw^o  essentially  dift"erent 
kinds.  Their  most  distinguished  exponents  were  Hal- 
LETT  of  Brighton  (England)  and  Rimpau  of  Schlanstedt 
(Saxony).    I  shall  now  endeavor  to  give  an  accottnt  of 

^  I  shall  deal  with  this  question  in  more  detail  in  §  14  of  this 
part. 


110    Selection  Does  Not  Lead  to  Origin  of  Species. 

their  methods,  so  far  as  the  space  at  my  disposal  al- 
lows. 

Hallett^  grew  his  pedigree  stock  under  the  most 
favorable  circumstances  possible  because  he  was  con- 
vinced that  manuring,  open  position  and  generally  favor- 
able conditions  of  life  call  forth  the 
variations  desired.  To  start  a  culture 
of  tliis  kind  he  sought,  in  the  best  field 
of  the  kind  of  wheat  in  question,  for 
the  best  ear  he  could  find  and  sowed  its 
seeds  in  good  garden  soil  as  early  as 
possible,  allowing  plenty  of  space  be- 
tween the  plants.  These  produced  strong 
richly  branched  plants  with  about  100 
stems  and  about  3000  grains  per  plant 

and  on  the  average  about  100  grains  per 

Fisf.  2?.  Scheme  to  a-i  •  ^  r  i 

show  the  relation  ^^^''      ^  ^^^^  extraordmary  advance  is  ne- 

between    the    se-  cessary    for    the    improvement   of    the 

lected    stock    and  .     .  .  ■  r     ^ 

the  so-called  com-  race,  but  it  IS  obviously  lost  if  the  new 

mercial    stock.        j.        -g  orrown  in  the  field  under  normal 
The    contmuous  ^ 

line   (E-E)   indi-  circumstances.      In   the    pedigree   stock 
cates   the   line   of   ,  .  .  ,         t^  .i  •     .i       i       . 

descent  of  the  for-  however  it  persists,     hrom  this  the  best 

mer,m  successive  g^j-g  on  the  best  plants  were  yearly  cho- 
years ;  the  dotted  .  ^  -^  •' 

lateral     branches  sen  with  the  greatest  care ;  and  of  these 

rectly  or^  in^  the  ^^^^^  ^"^  ^"^^  ^^^^  used  to  supply  seed  for 

course  of  a  year  the  continuation  of  the  experiment.    As 

or  two  the  com-  ,         -     ,  .  .        . 

mercial    stock,//,  a  result  of  this,   regular  improvements 

took  place   in  the  yield   and   Hallett 

believed   that   these   did   not   diminish   when   the   plants 

were  cultivated  in  the  field. 

There  is  no  question  that  improvement  takes  place 

*  Frederic  F.  Hallett,  On  Pcdigree-Wheaf  as  a  Mentis  of  In- 
creasing Crop.    Journal  of  the  Royal  Agricul.  Soc,  Febr.  1862, 


Cereals. 


Ill 


in  the  experimental  garden ;  the 
question  is  whether  this  is  main- 
tained in  the  field.  To  decide  this 
we  must  look  to  the  lateral  branches 
of  the  pedigree  which  are  given 
off  every  year,  in  which  the  seed  is 
increased  in  quantity  for  the  mar- 
ket as  explained  above.  It  is  not 
every  culture  that  succeeds  (e.  g., 
the  Original  Red  Wheat)  ;  but  it 
is  only  about  the  successes  that 
records  are  published. 

The  value  of  Hallett's  work 
is  proved  by  the  commercial  suc- 
cess of  his  races.  ^  But  he  seldom 
gives  data  of  any  value  for  scien- 
tific purposes.  Several  of  his  pro- 
ductions have  found  a  wide  sale, 
especially  in  England,  as  for  ex- 
ample Hallett's  Pedigree  wheat, 
Victoria  White  and  Golden  drop, 
three  famous  varieties  of  wheat. 
His  Chevalier  barley  and  his  two 
kinds  of  oats  Pedigree  White  Ca- 
nadian and  Pedigree  Black  Tar- 
tarian are  also  well  known. 

Hallett  asserts  that,  for  each 
sort,  the  rate  of  improvement  grad- 
ualy  falls  off  year  by  year  until  at 
the  end  of  many  years  the  race 
reaches  its  maximum  and  becomes 


a 


f  ^  9 

I  a  • 


Fig.  24.  H allett's  Ped- 
igree Wheat,  viewed 
from  the  narrow  and 
from  the  broad  side. 
Below  are  shown  (a^ 
grains  from  the  ears 
of  this  wheat  and  (b) 
grains  of  ordinary 
wheat  (compare  Fig. 
21,  p.  97-) 


1868. 


^Pedigree  alone  has  increased  my  cro[)s  from  25-30%.    Hallett, 


112    Selection  Does  Not  Lead  to  Origin  of  Species. 


constant.     But  of  course  it  will  not  remain  so,  if  it  is 
not  subjected  to  continuous  selection. 

RiMPAu's  method  is 
quite  different.  He  grew 
his  pedigree  stock  under 
circumstances  which  re- 
semble the  normal  condi- 
tions of  life  in  the  fields 
as  closely  as  possible.  The 
plants  were  however  grown 
somewhat  further  apart 
and  were  treated  with 
greater  care.  At  the  be- 
ginning of  the  experiment 
he  plucked  a  hand  full  of 
the  best  ears,  sowed  them 
on  a  small  plot  set  apart 
for  the  purpose  and  picked 
the  best  ears  from  this  at 
harvest  time,  for  seed  for 
the  next  elite  generation. 

RiMPAU  and  von  Rum- 
KER  insist  very  strongly 
that  plants  grown  under 
unusually  favorable  cir- 
cumstances should  not  be 
chosen  for  selection ;  ears 
found  at  the  edges  of  fields 
or  on  specially  luxuriant 
patches  should  most  cer- 
tainly not  be  used  for  this 
purpose.-^       Their    proper- 

^VoN  RiJMKER,  Gctrcidcziichtung,  1889,  p.  58. 


Fig.  25.  Schlanstedt  Giant  Rye, 
bred  by  W.  Rimpau.  b.  Grains 
of  this  strain  ;  c.  ordinary  grains 
of  rye  on  the  same  scale  of  re- 
duction. 


Cereals.  113 

ties,  however  desirable,  are  not  heritable.  I  have  failed 
to  ascertain  whether  this  opinion,  which  is  so  strongly 
in  opposition  to  Hallett's  has  been  arrived  at  as  the 
result  of  experiment.  But  it  is  obvious  that  the  progeny 
of  the  ears  picked  at  the  edge  of  the  field  or  in  luxuriant 
patches  would  require  similar  conditions  of  space  and 
soil  for  their  full  development,  and  as  they  would  not 
get  them  we  should  be  raising  a  variety  that  was  not 
adapted  to  its  environment.  For  the  improvement  of 
races  consists  primarily  in  the  adaptation  of  the  plants 
to  the  conditions  in  which  they  live ;  the  real  point  about 
modern  strains  of  cereals  is  that  they  can  get  more  out 
of  the  amount  of  manure  which  is  usually  applied,  than 
the  old  strains.  A  race  is  of  little  value  except  under 
those  particular  conditions  to  which  it  is  adapted;  how 
far  it  will  spread  in  general  cultivation  depends  on  how 
widely  distributed  these  conditions  are. 

There  is  therefore  a  greater  likelihood  of  raising  a 
valuable  race  by  Rimpau^s  method,  than  by  Hallett's; 
but  it  takes  a  longer  time  to  arrive  at  the  result.  And 
even  Rimpau  did  not  succeed  with  every  attempt;  for 
example  he  states  that  he  spent  a  great  deal  of  vain  labor 
in  trying  to  improve  the  ordinary  brown  saxon  wdieat  by 
his  method.^ 

RiMPAu's  Schlanstedt  Rye  is  well  known  to  every 
farmer.^  He  began  working  with  it  in  1867.  When 
I  visited  Rimpau  on  his  estate  at  Schlanstedt  in  1876  he 
showed  me  his  pedigree  culture  which  even  then  fur- 
nished the  seed  for  the  greater  part  of  his  domain.  Since 
1886  he  has  been  in  a  position  to  sell  his  whole  harvest 
as  seed.^    The  race  has  general  recognition  and  has  con- 

^  RiSLER^s  Wehenbaii,  p.  66  note. 
'^  V.  RiJMKER,  Gctreideziichtung,  p.  74  .  ''  Weisenhau,  pp.  65-66. 


114    Selection  Docs  Not  Lead  to  Origin  of  Species. 

sequently  extended  over  Germany  and  the  north  of 
France/  and  is  now  admitted  to  be  one  of  the  best  Euro- 
pean cereals.^  Ears  and  grains  are  about  twice  the  size 
of  those  of  other  sorts  of  rye;  they  ripen  earher  and, 
what  is  far  more  important,  give  a  much  larger  return 
per  acre.'^ 

In  this  case  as  in  the  previous  ones,  incessant  selec- 
tion and  plenty  of  manure  are  the  conditions  which  are 
necessary  to  keep  the  race  at  the  level  which  it  has 
reached.  Avidity  for  manure  is,  according  to  Risler- 
RiMPAU,  a  feature  which  distinguishes  improved  races 
from  constant  varieties.^ 

This  improvement  of  races, ^  as  now  practised  in 
agriculture,  has,  however,  of  late  appeared  in  a  wholly 
different  light  through  the  practical  researches  of  Dr. 
HjALMAR  NiLSSON  of  the  Swedish  Agricultural  Experi- 
ment Station  at  Svalof.^ 

He  discovered  that  cereals  and  other  agricultural 
crops  consist  of  far  larger  numbers  of  elementary  spe- 
cies, than  was  hitherto  supposed.  Out  of  every  so-called 
variety  hundreds  of  such  minor  types  can  be  isolated, 
which  as  a  rule  prove  constant  at  once  after  such  isola- 
tion. Exceptions  are  offered  by  casual  hybrids,  which 
may  split  up,  after  which  the  products  may,   however, 

*  ScHRiBAUX,  Seigle  de  Schlanstedt,  Almanach  du  Cultivateur, 
1892,  p.  66. 

^  See,  e.  g.,  the  seed  catalogue  of  Vilmorin-Andrieux  in  Paris. 

^  The  rye  of  Rimpau  has  since  been  surpassed  by  that  of  Pctkus, 
produced  by  Von  Lochow  (Note  of  1908). 

*  Weizenhaii,  p.  80. 

^  The  following  paragraphs  were  added  to  the  translation,  1908. 

*  Cf.  Sveriges  Utsddes  forcnings  Tidskriff,  Years  1892-1907,  Vol. 
T-XVI,  and  Die  Svalofcr  Mcthodc  zur  Veredlitng  landivirthschaft- 
licher  Kiiltiirgewdchse  und  ihrc  Bedeutung  fiir  die  Selektionstheovie, 
Archiv  fiir  Rassen-  und  Gesellschafts-Biologie.  Jahrg.  3,  pp.  325-358. 
1906. 


Cereals.  115 

also  give  rise  to  constant  races.  Within  each  cukivated 
variety  the  number  of  differentiating  characters  may 
be  small,  but  the  large  number  of  elementary  forms  may 
be  due  mainly  to  the  vast  number  of  ways  in  which  they 
may  be  combined.  Probably  these  subspecies  have 
arisen  in  the  fields  by  casual  mutations  and  subsequent 
free  crossing;  such  crosses  being,  as  a  matter  of  fact, 
very  rare,  but  occurring  often  enough  to  give  rise  in  the 
lapse  of  years  to  almost  all  possible  combinations  of 
characters. 

The  diversity  among  these  elementary  forms  is  so 
large,  that  it  answers  almost  all  the  claims  of  practice. 
This  fact  is  of  the  highest  practical  interest,  since  now 
it  is  only  necessary  to  search  for  the  desired  types,  to 
isolate  them,  to  estimate  their  value  and  to  multiply  them 
to  the  amount  required.  No  slow  improvement,  no  re- 
peated selection  is  necessary ;  the  fluctuating  variability 
within  the  elementary  species  being  moreover  so  small, 
as  hardly  to  afford  material  for  such  work. 

This  search  for  useful  elementary  types  must  be  car- 
ried on  in  the  fields  at  the  time  just  before  the  harvest. 
The  ripe  ears  are  selected  and  their  grains  sown  sepa- 
rately for  each  parent-plant.  From  these  the  new  races 
are  started.  At  the  time  mentioned  manv  valuable  char- 
acters  can  be  judged,  but  others  cannot,  or  cannot  be 
estimated  with  a  sufficient  degree  of  accuracy.  This 
difficulty,  however,  has  been  met  by  another  discovery 
of  NiLSSON,^  viz.,  the  correlation  between  botanical  and 
agricultural  characters.  On  the  ground  of  this,  the  first 
selection  is  made  by  the  aid  of  botanical  marks,  which 
are  discernible  in  the  ripe  ears,  and  the  subsequent  com- 

^  For  more  details  see  Plant-Breeding,  Comments  on  the  Experi- 
ments of  Nilsson  and  Bnrbank.  Chicago,  1907. 


116    Selection  Does  Not  Lead  to  Origin  of  Species. 

parative  study  of  the  isolated  races  is  made  by  both 
botanical  and  economically  valuable  characters.  Hun- 
dreds of  different  types  can  be  isolated  from  the  harvest 
of  a  field  in  this  way  if  one  is  only  thoroughly  acquainted 
with  the  correlative  value  of  these  apparently  unimpor- 
tant characters.  For  instance  the  propensity  towards  lay- 
ering may  be  estimated  by  the  density  of  the  ears ;  short- 
ness of  internodes  being  closely  correlated  with  stiffness 
of  halms.  The  value  of  barley  for  the  purposes  of  the 
brewers  is  indicated  by  the  kind  of  hair  on  the  scales, 
crisp  hairs  denoting  the  best  qualities  of  the  grain.  On 
the  basis  of  this  correlation  a  new  brewers'  barley  has 
been  isolated  at  Svalof,  not  from  the  ordinary  Chevalier- 
barley,  which  is  much  subject  to  layering  in  Sweden,  but 
from  the  Imperial  barley,  which  is  not  a  brewers'  barley 
at  all  but  has  very  stiff  halms.  This  new  type  answers 
the  demand  of  practice  especially  in  Middle  Sweden, 
where  it  is  now  almost  exclusively  cultivated  for  this 
purpose.     It  is  called  Svalof  Primus  Barley. 

Correlation,  as  understood  at  Svalof,  does  not  mean 
that  two  characters  are  inseparable,  but  only  that  they 
are  found  to  accompany  each  other  in  the  majority  of  the 
cases,  i.  e.,  in  90  out  of  100  instances.  Mother-plants 
selected  in  this  way,  have  therefore  to  be  subjected  to  a 
subsequent  selection  by  means  of  their  progeny. 

The  new  races,  which  have  been  isolated  and  put  on 
the  market  from  Svalof  in  this  way  include  7  types  of 
winter  wheat,  1  of  summerwheat,  8  of  barley,  5  of  wdiite 
oats,  2  of  black  oats,  4  peas  and  3  vetches.  The  first  of 
them  was  brought  out  in  the  year  1897.  Numerous  new 
types  have  since  been  isolated  but  are  as  yet,  still  in  prep- 
aration. 

Bv  means   of  these   facts   the   common   ae^ricultural 


Cereals.  117 

method  of  repeated  selection  and  slow  improvement  may 
be  explained  in  a  way  which  shows  its  complete  agree- 
ment with  the  theory  of  mutation.^ 

Such  a  selection  was  begun  by  choosing  a  handful  of 
ears  from  the  best  specimens  of  the  variety  which  it  was 
intended  to  improve.  From  these  a  race  was  started,  in 
which  the  selection  was  repeated  every  year  on  the  same 
principles.  But  according  to  the  discoveries  of  Nilsson 
the  first  handful  of  ears  must  have  been  far  from  uni- 
form; in  fact  it  must  have  contained  almost  as  many  dif- 
ferent types  as  there  were  ears.  For  even  after  a  selec- 
tion by  the  elaborated  methods  now  in  use  at  Svalof,  two 
'  apparently  similar  ears  may  give  rise  to  wdiolly  different 
races.  In  former  years  the  similarity  of  the  best  ears 
chosen  from  a  field,  was  therefore  erroneously  expected 
to  give  a  uniform  result. 

From  this  point  of  view  the  real  meaning  of  the  sub- 
sequent repeated  selection  at  once  becomes  clear.  Every 
year,  from  among  the  motley  group,  those  ears  were 
chosen  which  most  closely  approached  the  ideal.  In  this 
way,  slowly  but  surely,  the  mixture  must  become  purified, 
till  at  last,  after  perhaps  10  or  20  years,  it  was  reduced 
to  only  one  of  the  constituent  types  of  the  first  choice. 
As  soon  as  this  stage  was  reached,  the  race  was  pure  and 
constant  and  independent  of  further  selection,  which  now 
only  played  the  role  of  permanently  keeping  it  in  a  pure 
condition. 

The  slow  improvement  of  agricultural  races,  which 
played  such  a  large  part  in  the  selection  theory  of  Dar- 

^  Elementary  Species  in  Agriculture,  Proceed.  Americ.  Philos, 
Soc,  Vol.  XLVT,  1908,  p.  149.  Cf.  also:  Aeltere  und  neucre  Sclck- 
tionsmethodc,  Biol.  Centralbl.  XXVI,  No.  13-15,  1906;  La  thcorie 
darwinienne  et  la  selection  en  agriculture,  Revue  scientiflque,  5e  Serie, 
Tome  V,  p.  445,  1906,  and  Neiv  Principles  in  Agricultural  Plant- 
Breeding,  The  Monist,  Chicago,  1907,  p.  209. 


118    Selection  Does  Not  Lead  to  Origin  of  Species. 

WIN  IS  thereby  sliown  to  be  only  apparent.  In  reality 
it  is  only  an  isolation  of  previously  constant  types.  From 
horticultural  practice  it  only  differs  by  the  fact  that  the 
races  to  be  isolated  are  old  constituents  of  long  cultivated 
mixtures  whereas  in  horticulture  mutations  are  usually 
isolated  as  soon  as  they  appear. 


§  13.  THE  LIMITS  TO  THE  AMOUNT  OF  CHANGE  THAT 
CAN  BE  EFFECTED  BY  SELECTION. 

Selection  does  not  lead  to  the  origin  of  specific  char- 
acters.^ If  I  have  succeeded  in  showing  that  this  general- 
ization is  in  accord  with  the  facts  of  plant-breeding,  the 
chief  support  of  the  doctrine  of  selection  has  been  under- 
mined. I  propose  therefore  to  summarize  the  most  im- 
portant parts  of  my  argument  in  a  series  of  short  para- 
graphs. 

1.  Linear  Variation.  Statistical  methods  of  dealing 
with  variability  are  so  generally  employed  at  the  present 
time  that  an  acquaintance  with  their  principles  may  be 
taken  for  granted.  The  chief  thing  however  that  we 
learn  from  these  curves  is  that  the  characters  vary  only 
in  two  directions:  plus  and  minus.  The  old-fashioned 
vague  talk  about  variation  of  single  characters  in  all 
directions  has  died  a  natural  death.  All  variations  in 
mass,  and  weight,  and  number  (meristic  variations)  con- 
form to  this  law.      ^ 

The  character  can  be  diminished  or  increased,  but 
nothing  new  can  arise  in  this  way.  The  differentiation 
of  organisms  in  the  main  lines  of  descent  consists  in  the 
development  of  new  characters ;  and  the  materials   for 

^  In  men  abnormal  characters  fluctuate:  but  they  soon  disappear 
and  no  new  monstrous  variety  arises.  See  Kollmann  in  Correspon- 
densblatt  d.  deutsch  .Ges.  f.  Anthropologic,  1900,  No.  i,  p.  3. 


Limits  to  the  Effects  of  Selection.  119 

this  are  not  supplied  by  the  Hnear  variation  of  characters 
which  are  already  present. 

2.  The  Duration  of  Progress.  The  view  that  linear 
variation  is  unlimited  in  the  sense  that  the  changes  which 
can  be  brought  about  by  selection  in  the  course  of  cen- 
turies are  greater  than  those  which  can  be  attained  in  the 
course  of  a  few  years,  is  absolutely  without  foundation. 
We  are  speaking  of  course  of  the  improvement  of  a 
single  character  considered  by  itself.  As  a  matter  of  fact, 
2  or  3  years  under  favorable  conditions,  or  3  to  5  under 
ordinary  ones,  are  quite  sufficient.  The  further  prosecu- 
tion of  selection  serves  merely  to  keep  the  race  at  the 
level  which  it  had  reached,  unless  special  circumstances 
arise  (see  sections  6  and  7). 

3.  The  Limits  of  Selection.  There  is  just  as  definite 
a  limit  to  selection  as  there  is  to  linear  variation.  The 
limits  of  the  latter  can  be  extended  by  dealing  with  a 
greater  number  of  individuals;  but  it  takes  an  enormous 
increase  in  this  number  to  sensibly  extend  these  limits. 
It  is  the  same  with  selection;  but  this  at  least  has  the 
advantage  that  the  number  of  individuals  dealt  with  can 
be  diminished  by  discarding  those  of  no  value. 

It  is  often  stated  that  variation  in  a  given  direction 
can  be  increased  bv  selection  in  that  direction.  Observa- 
tions,  or  exact  information  in  support  of  this  statement 
are  not  given.  There  is  of  course  an  appearance  of 
change  owing  to  the  elimination  of  the  less  valuable 
individuals.  As  a  matter  of  fact  in  accuratelv  recorded 
cases  the  very  reverse  is  found  to  be  the  case ;  that  is  to 
say,  that  it  becomes  gradually  more  difficult  to  effect  any 
change  until  finally  it  becomes  impossible. 

Darwin''s  view  that  plants  increase  in  variability  in 
the  first  years  after  they  are  brought  into  cultivation 


120    Selection  Does  Not  Lead  to  Origin  of  Species. 

probably  owes  its  origin  partly  to  the  fact  that  the  num- 
ber of  individuals  is  vastly  increased  during  that  period 
and  partly  to  the  frequent  discovery  of  subspecies  which 
previously  had  been  overlooked. 

4.  Regression.  Selection  is  succeeded  by  regression, 
which  is  great  in  proportion  to  the  stringency  of  the 
selection  which  preceded  it.  However  long  the  selection 
is  maintained  it  is  always  follow^ed  by  regression.  It 
appears  that  much  more  than  half  of  wdiat  was  gained 
is  lost  after  cessation  of  selection.  The  mean  of  the 
character  so  far  as  we  know^  cannot  be  altered ;  regression 
always  aims  at  the  bull's  eye  of  the  specific  character. 
I  shall  return  to  this  point  in  the  next  section. 

We  may  lay  it  down  as  a  general  rule  that  a  doubling 
or  a  halving  of  the  original  mean  is  about  the  most  that 
can  be  attained  by  selection.  And  usually  one  has  to  put 
up  with  much  more  meagre  improvement.-  The  most 
conspicuous  case  of  variability  is  the  increase  in  fleshi- 
ness in  fruits  and  roots,  but  this  exception  is  only  ap- 
parent.^ 

5.  The  Instability  of  Races.  The  chief  difference 
between  improved  races  and  species,  even  the  smallest 
elementary  species,  is  the  instability  of  the  former  and 
the  stability  of  the  latter.  Races  that  have  arisen  by 
selection  can  only  be  preserved  by  continuing  that  pro- 
cess; it  costs  as  much  trouble  to  retain  them  as  it  did 
to  obtain  them.  If  selection  of  the  race  ceases,  the  char- 
acters of  the  race  fade  away.  And  the  time  it  takes 
them  to  disappear  is  the  same  as  it  took  them  to  appear. 
In  a  few  generations  they  come ;  in  a  few  also  do  they  go. 

^Compare  the  figures  given  in  Wallace's  Darzvinism,  p.  8i. 
''  The  crab  apple  is  more  than  half  the  size  of  most  of  our  eating 


apples 


Limits  to  the  Effect  of  Selection.  121 

6.  Continual  Improvement  of  the  Method  of  Selec- 
tion. Commercial  considerations  demand  a  continual 
progress,  partly  in  the  actual  improvement  of  stock, 
partly  for  the  purposes  of  advertisement  in  order  not 
to  be  eclipsed  by  competitors.  This  progress  is  effected 
in  many  ways,  among  which  the  most  important  from  our 
point  of  view  are  the  improvement  of  the  method  of  se- 
lection and  the  practice  of  breeding  with  as  many  char- 
acters as  possible  in  view  at  once.  Every  improvement 
in  method  renders  a  more  effective  selection  feasible.  But 
if  after  this  the  selection  remains  constant  no  further  ad- 
vance is  possible. 

7.  Improvement  in  Many  Directions.  A  scientific  in- 
vestigation should,  if  possible,  be  restricted  to  a  single 
character.  But  the  laws  of  correlation  seldom  allow  us 
to  follow  this  rule.  Besides,  the  conditions  of  our  in- 
vestigations exert  an  unconscious  selection  in  the  garden, 
analogous  to  the  so-called  natural  selection  in  the  fields, 
inasmuch  as  the  stronger  manage  to  flower  while  the 
weaker  do  not.  The  practical  breeder  on  the  other  hand 
pays  attention  to  as  many  features  as  possible.  And  that 
is  the  chief  reason  why  his  experiments  last  so  much 
longer.  For  it  is  not  difficult  to  see  that  with  a  limited 
number  of  individuals  it  takes  twice  as  many  generations 
to  deal  with  two  characters  as  it  does  to  deal  with  one. 
The  greater  the  number  of  characters  we  handle,  the 
slower  shall  we  be  in  attaining  our  result. 

8.  Adaptation  to  Special  Conditions  of  Cidtivation. 
Ever}^  improved  race  is  adapted  to  a  special  environment, 
of  soil,  climate  and  manure.  That  is  why  they  are  so 
local  in  their  distribution  and  so  fastidious.  Many  Eng- 
lish races  cannot  stand  the  German  climate ;  the  majority 
of  American  fruit  trees  do  not  thrive  in  England,  and  so 


122    Selection  Does  Not  Lead  to  Origin  of  Species. 

forth.  Many  races  are  no  good  except  in  small  districts, 
and  sometimes  even  on  single  farms.  Each  race  has  its 
own  taste  in  the  matter  of  soil  and  manure,  and  we  can 
only  count  on  the  expected  harvest  when  this  taste  is 
satisfied.  They  behave  in  just  the  same  way  as  the  local 
races  of  our  wild  flowers. 

9.  Natural  Selection  in  the  Field.  Much  too  little 
attention  is  usually  paid  by  the  biologist  to  this  phenom- 
enon although  it  is  of  such  tremendous  practical  im- 
portance. Cold,  frost,  moisture,  crowding  together  and 
late  ripening  select  as  effectively  in  the  field  as  the  most 
vigilant  husbandman.  Sometimes  they  cooperate  with 
him  but  generally  they  are  opposed  to  him.  In  the  case 
of  acclimatization  they  are  usually  on  the  same  side  in- 
asmuch as  the  new  climate  only  spares  those  individuals 
which  can  stand  it.  And  the  same  is  true  of  the  effort 
to  keep  up  old-established  races  of  any  particular  country. 
In  the  cultivation  of  the  better  sorts  and  in  empirical 
selection  the  work  of  the  breeder  might  well  be  said  to 
consist  simply  in  suspending  the  action  of  natural  selec- 
tion. If  nature  and  art  have  equal  weight  in  the  balance 
the  value  of  the  race  does  not  change.  In  methodical 
selection  of  improved  races  nature  almost  always  works 
against  the  breeder  by  favoring  the  stronger  and  coarser 
individuals.  The  breeder's  task  is  therefore  first  to  main- 
tain his  race  and  then  to  improve  it. 

§  14.  THE  BEHAVIOR  OF  IMPROVED  RACES  AFTER  THE 

CESSATION  OF  SELECTION. 

As  soon  as  selection  ceases  the  qualities  of  an  im- 
proved race  disappear.  That  which  has  been  attained 
by  the  work  of  many  years  may  disappear  in  a  few  gen- 
erations.     The  most   experienced   breeders   express   the 


Improved  Races  After  Selection  Ceases.         123 

opinion  that  selection  must  not  be  neglected  even  in  a 
single  generation.  Moreover  whatever  principle  of  se- 
lection is  adopted,  must  be  adhered  to  throughout  if  any- 
thing is  to  be  attained. 

Only  a  few  years  are  necessary  for  a  complete  retro- 
gression. And  no  amount  of  selection  can  prevent  this 
retrogression  or  even  diminish  its  influence.  The  breeder, 
with  infinite  labor  and  patience,  and  working  with  a  large 
number  of  individuals,  fixes  his  attention  on,  and  im- 
proves a  certain  set  of  characters.  Then  nature  comes, 
lays  her  hands  on  all  the  features  of  the  race  and  elimi- 
nates those  which  even  in  the  slightest  degree  reduce  the 
strength  of  the  plant. 

*'The  more  a  race  has  been  improved  the  less  will  it 
bear  a  cessation  of  selection,"  says  Von  Rumker  at  the 
end  of  his  instructive  discussion  of  this  difficult  problem.^ 
Continued  selection  by  no  means  fixes  the  character 
chosen,  but,  by  separating  the  race  further  from  the 
type  from  which  it  sprang,  continually  adds  to  the  risk 
of  regression.  The  maintenance  of  an  improvement 
depends  on  the  continuation  of  selection;  for  nature  is 
continually  striving  to  reduce  the  new  mean  to  the  orig- 
inal one.  This  mean  is  a  state  of  equilibrium  from 
which  skilful  practice  can  only  temporarily  raise  the  char- 
acters of  a  plant. 

There  are  certain  experiments  on  the  reversal  of 
selection  which  are  worthy  of  our  attention. 

Peas  which  have  been  cultivated  for  many  years  on 
a  warm  dry  soil  regularly  ripen  their  seeds  in  a  short 
time — often  about  forty  days;  but  if  they  are  sown  in 
another  soil  they  preserve  their  property  of  early  ripen- 

^  Von  Rumker,  Anleitung  aur  Cefreidcciichfnng.  1889,  P-  8r.  See 
also  LiNDLEY,  Theory  of  Horticulture,  1840,  p.  314. 


124    Selection  Does  Not  Lead  to  Origin  of  Species. 

ing  for  the  first  year  only,  but  in  succeeding  years  become 
later  and  later.  ^ 

Then  there  is  the  well-known  case  of  Buckman  who 
by  reversing  selection  for  a  few  generations  converted 
the  cultivated  parsnip  into  the  wild  form  (Pastiiiaca 
sativa).  Watson  obtained  the  same  result  with  the 
Scottish  cabbage  in  three  generations.  Darwin's  verdict 
on  this  point  is  that  a  period  of  selection  which  need 
not  extend  over  many  generations  would  be  sufficient  to 
convert  most  of  our  cultivated  plants  into  wild  or  nearly 
wild  forms. 

I  have  already  mentioned  Schubeler's  experiments 
on  the  extension  of  the  northern  limit  of  the  culture  of 
cereals  in  Norway.  He  found  that  if  he  took  the  forms 
which  have  been  grown  at  the  northern  limit — that  is. 
the  short  lived  forms — back  to  their  native  place  after 
a  few  years,  that  they  ripened  earlier  and  bore  heavier 
seeds  than  those  forms  of  the  same  sort  which  had  re- 
mained there  all  the  time;  but  that  after  a  few  genera- 
tions this  distinction  vanished. 

Fruit  trees  grown  from  seed  quickly  revert  to  the 
original  type;  the  Olive  to  the  Oleaster;  apples  and  pears 
give  smaller  and  less  juicy  fruit;  and  chestnuts  become 
quite  unpalatable.^  But  our  information  on  these  phe- 
nomena is  far  too  meagre. 

If  it  was  not  a  so-called  species  but  a  subspecies 
which  was  subjected  to  improvement,  the  new  form  re- 
turns, on  cessation  of  selection,  not  to  that  of  the  spe- 
cies, but  to  the  mean  of  the  subspecies.  Double  balsams 
and  buttercups  tend  to  become  single,  Triticitm  coin- 
posittmi  turgidimi  (Fig.  26)  becomes  less  branched,  the 

*  Darwin,  Das  Variiren,  II.  p.  42. 

^De  Candolle,  Originc  dcs  Planfes  cultivccs,  p.  372. 


Improved  Races  After  Selection  Ceases.         125 


cockscoml^s,  Celosia  cristata,  become  much  less  flattened ; 
but  the  doubling,  branching  and  fasciation  are  never  en- 
tirely lost  and  if  single  individ- 
uals should  seem  to  lack  them, 
they  will  always  reappear  in 
plants  grown  from  their  seed. 
The  same  conditions  obtain  in 
my  experiments  with  Papaver 
somnifcrum  polycephaluin  and 
in  Tri folium  pratense  quinque- 
foliuin.  On  the  cessation  of  se- 
lection these  plants  lose  the  high 
pitch  of  their  improvement  but 
not  the  character  itself. 

I  have  already  referred  (pp. 
72-73,  Figs.  17  and  18)  to  my 
experiment  with  maize.  Starting 
in  1886  with  an  ordinary  race 
of  maize  whose  average  number 
of  rows  varied  between  12  and 
14,  I  had  succeeded  by  1891  in 
raising  a  race  with  a  mean  of  20 
rows,  a  number  which  the  orig- 
inal hardly  ever  reached  From 
1892-6  the  race  was  maintained 
by  selection  at  about  the  same 
level.  During  the  period  1897- 
1899  however  I  selected  the  ears 
with  the  smallest  number  of 
rows.  In  1897  I  sowed  the  seeds 
of  a  16-rowed  ear,  but  the  mean 

of  the  harvest  which  they  bore  lay  still  at  20.     The  next 
year,   1898,  the  mean  lay  at  18,  and  in   1899  at   14-16 


Fig 


26.  Triticum  turgidum 
compositum,  branched 
Wonder  or  Smyrna 
Wheat. 


126    Selection  Does  Not  Lead  to  Origin  of  Species. 

rows.     In  three  years  therefore  the  effect  of  the  pre- 
vious selection  had  disappeared. 

The  Progeny  of  the  Original  Seed.  It  is  this  retro- 
gression which  attends  the  cessation  of  selection  which 
is,  as  we  have  already  said,  the  chief  difference  between 
highly  improved  agricultural  races  and  the  so-called  vari- 
eties or  subspecies.  The  rational  farmer  buys  his  seed 
from  that  source  in  which  it  has  been  brought  to  the 
highest  pitch  of  productiveness,  whether  this  has  happened 
by  empirical  or  methodical  selection  or  by  particularly 
favorable  conditions  of  climate  and  soil  which  act  as  a 
kind  of  natural  selection.  Such  stock  seed  is  of  course 
dear.  In  the  case  of  cereals  and  particularly  in  the  case 
of  flax,  the  custom  is  therefore  to  sow  the  bought  seed 
and  to  use  the  harvest  thus  raised  for  the  main  crop ; 
some  of  which  may  again  be  used  for  seed.^  But  the 
race  does  not  retain  its  good  qualities  longer  than  two 
generations ;  and  in  order  to  have  a  satisfactory  harvest 
it  is  necessary  to  replenish  the  stock  seed  from  time  to 
time. 

We  see  therefore  that  original  seed  and  its  progeny 
can  be  wholly  different  in  their  yield. ^  And  the  differ- 
ence is  great  in  proportion  as  the  conditions  of  cultiva- 
tion are  dissimilar  and  in  proportion  to  the  number  of 
generations  grown  from  the  same  lot  of  bought  seed. 
In  the  first  year  the  race  retains  its  good  qualities,  but 
as  soon  as  the  conditions  of  life  become  different  or  the 
care  spent  in  choosing  seed  for  next  year  becomes  less 
than  that  exercised  previously,  the  good  qualities  of  the 
race  begin  to  disappear. 

Change  of  Seed  is  a  practice  largely  carried  on  in 

^  Langethal,  Landzvirthschaftlichc  PHanzenkunde. 

^VoN  RiJMKER,  Der  zvirthschaftliche  Mehrwerth,  loc.  cit.,  p.  136. 


Improved  Races  After  Selection  Ceases.         127 

agriculture  and  horticulture.  There  is  a  great  deal  ul 
uncertainty  as  to  its  meaning;  but  it  probably  serves 
different  objects  in  different  places. 

In  the  best  known  cases  however  this  process  is  con- 
nected with  the  practice  of  home  growing  which  we 
have  just  been  considering.  The  small  farmer  and  the 
gardener  effect  this  change  by  making  it  a  practice  not 
to  save  seed  which  they  have  themselves  harvested  but  to 
buy  pedigree  seed  afresh.  This  custom  is  a  very  old  one. 
For  example  Hunting  said  as  long  ago  as  1671^  that 
the  home-grown  seed  of  cauliflower  and  savoys  gave  in- 
ferior results ;  and  that  seed  ought  to  be  procured  afresh 
from  Italian  sources.  Jordan  often  sowed  vegetable 
seeds  with  the  object  of  seeing  them  degenerate,  and 
regularly  observed  a  speedy  retrogression  to  the  wild 
type.^  LiNDLEY  states,  in  his  Theory  of  Horticulture, 
cited  above,  tliat  prominent  seedsmen  buy  the  seeds  for 
the  early  strains  of  their  annuals  from  warmer  and  drier 
districts. 

RiSLER  says  on  this  point'"^ :  "If  a  farmer  tries  to 
grow  varieties  of  wheat  which  do  very  well  elsewhere 
but  are  new  to  him  and  to  his  district  he  is  doing  the 
reverse  of  selection."  Varieties  are  adapted  to  the  soil 
and  to  the  climate  of  their  original  home.  If  they  are 
introduced  in  due  time  we  may  expect  to  reap  the  re- 
ward of  the  labor  that  has  been  spent  in  their  perfection ; 
but  they  will  not  last  indefinitely  if  the  conditions  in 
which  they  are  grown  are  not  at  least  tolerably  similar 
to  those  from  which  they  came. 

In   1894,  J.   H.   VAN   Mansholt,   one  of  the  most 

^  Abraham  Munting,  Waare  Ocffeninge  der  Planten,  p.  319. 
'  Arbres  f  rut  tiers,  1853,  P-  57- 
"  Weisenhau,  p.  79. 


128    Selection  Does  Not  Lead  to  Origin  of  Species. 

prominent  breeders  in  the  Netherlands,  has  written  an 
account  of  this  practice  as  followed  in  his  country.  There 
are  certain  districts  in  which  particular  kinds  of  cereals 
retain  their  valuable  characters  unimpaired  and  from 
these  other  less  fortunate  districts  obtain  their  seed.  For 
example  the  Zeeland  wheat  only  retains  its  beautiful 
white  color  in  Zeeland;  in  Groningen  and  Friesland  this 
character  is  lost  in  a  few  generations.  Flax  seeds  are 
obtained  from  Riga  and  only  quite  exceptionally  can 
they  be  grown  witliout  renewal  for  more  than  three 
or  four  years ;  for  degeneration  soon  sets  in,  especially 
in  respect  of  resistance  to  disease.  A  whole  list  of  fur- 
ther examples  leads  us  to  the  conclusion  that  repeated 
purchase  of  new  seed  stock  from  better  localities  is  ab- 
solutely indispensable  in  the  less  favored  districts. 

The  so-called  process  of  ''Intermediate  Generations" 
is  adopted  in  the  case  of  the  sugar  beet  especially.  One 
or  at  most  two  generations  are  interpolated  between  the 
liarvest  of  the  seeds  of  polarized  beets  and  the  seed  for 
sale.  The  object  is  to  cover  the  cost — which  is  very 
high — of  the  polarization  process  and  of  selection,  by 
vastly  increasing  the  amount  of  seed  for  sale. 

The  more  drastically  selection  is  carried  out  the 
smaller  does  the  number  of  select  beets  become  and,  con- 
sequently, also  the  amount  of  seed  that  can  be  obtained 
from  them.  It  is  necessary  therefore  to  increase  the 
quantity  of  seed,  and,  moreover,  to  do  this  in  short  time 
in  order  to  reduce  the  amount  of  degeneration,  due  to 
the  interpolation  of  many  generations,  to  a  minimum. 
A  very  curious  method  is  adopted  to  effect  this.  The 
seed  plants  are  not  sown  the  usual  distance  apart  but  so 
close  that  the  beets  are  only  as  thick  as  one's  finger.  The 
result  of  this  is  that  the  stem  is  only  slightly  branched 


Improved  Races  After  Selection  Ceases.         129 

and  ripens  only  the  best  seeds;  for  the  seeds  which  are 
borne  on  the  weaker  lateral  branches  with  which  normal 
beet  plants  are  covered  are  well  known  to  be  poorer. 
This  method  results  in  a  far  more  stringent  selection 
of  seeds  than  can  be  effected  by  means  of  sieves  or  centrif- 
ugal machines ;  and  it  seems  that  this  selection  wholly 
or  almost  wholly  counteracts  the  ill  effects  of  degenera- 
tion resulting  from  the  cessation  of  selection. 

Intermediate  generations  are  often  indispensable,  es- 
pecially in  the  case  of  cereals.  For  it  is  obvious  that  in 
races  in  which  the  pedigree  stock  is  small,  but  for  which 
the  demand  is  great,  an  enormous  increase  in  the  amount 
of  seed  must  be  brought  about  before  the  seed  can  be 
put  on  the  market.  But  no  race  will  stand  more  than  2 
or  at  most  3  intermediate  generations.  Moreover  if  this 
process  is  not  carried  out  with  the  greatest  care  the  value 
of  the  race  is  lost. 

Conclusion.  The  instability  of  races  is  the  central 
fact  on  which  all  agricultural  breeding  processes  are 
based.  The  seed  on  the  market  is  always  inferior  to 
pedigree  seed,  if  not  in  the  first  generation,  at  any  rate 
regularly  in  the  second  or  third.  And  no  matter  how 
long  selection  is  carried  on  it  cannot  remove  this  in- 
feriority. 


IV.   CONTROVERSIAL  QUESTIONS. 

§    15.   ACQUIRED    CHARACTERS    AND   VARIATIONS 
CAUSED  BY   NUTRITION. 

It  is  not  my  intention  to  enter  into  a  discussion  of 
the  much  disputed  question  of  the  inheritance  of  acquired 
characters.  I  only  wish  to  show  how  a  clear  understand- 
ing of  the  difference  between  the  theory  of  selection  and 
the  theory  of  mutation  to  a  great  extent  simplifies,  and 
may  perhaps  even  lead  to  a  satisfactory  solution  of,  this 
problem. 

The  point  at  issue  is  really  one  of  definition.  Each 
author's  conclusion  on  this  question  depends  on  the  defi- 
nition of  "acquired"  with  which  he  starts. 

Starting  as  we  can,  after  the  discussion  in  the  last 
chapter,  with  an  insight  into  the  nature  of  selection  and 
of  improved  races,  let  us  formulate  as  clearly  as  possible 
what  the  question  for  decision  really  is. 

Mutations  obviously  do  not  fall  within  the  category 
of  acquired  characters.  There  can,  it  seems  to  me,  be 
no  doubt  about  this.  They  appear  suddenly ;  w^e  can  as 
yet  assign  no  cause  for  them ;  they  seem  independent  of 
the  environment.  They  are  germinal  variations  in  the 
strictest  sense  of  the  term. 

According  to  the  mutation  hypothesis  species  have 
arisen  by  such  mutations.  Therefore  specific  characters 
are  never  "acquired";  and  there  is  therefore  no  need  for 


Acquired  Characters  and  Effects  of  Nutrition.  131 

taking  ''acquired  characters"  into  consideration  in  the 
whole  domain  of  comparative  biology  and  the  theory  of 
descent. 

The  study  of  these  characters  falls  within  the  prov- 
ince of  variability  in  the  restricted  sense — in  that  of  indi- 
vidual or  fluctuating  variability.  It  lies  within  the  limits 
of  the  species  themselves  even  when  these  limits  are  so 
narrow  that  they  serve  merely  to  separate  the  elementary 
species  from  one  another. 

But  within  these  limits  there  is  heredity.^  The  family 
character,  the  improved  races  of  the  breeder  and  the  few 
scientific  experiments  in  selection  that  exist  prove  this 
up  to  the  hilt. 

Are  these  variations  brought  about  by  external  or 
internal  causes?  Ploetz  says,  ''the  causes  must  of  course 
be  sought  ultimately  in  external  influences."-  The  bio- 
metrician  finds  it  simpler  to  suppose  that  it  is  indepen- 
dent of  the  environment  and  is  not  causally  connected 
with  any  alteration  in  the  external  conditions  of  life.'"^ 
But  such  an  assumption  is  obviously  only  a  preliminary 
step,  made  only  to  insure  simplicity  in  the  treatment  of 
the  phenomena   investigated. 

There  is  much  evidence  to  show  that  individual  vari- 
ations are  occasioned  by  external  influences.  And  if  this 
is  so  we  should  be  justified  in  regarding  individual  vari- 
ations as  acquired  qualities.     For  most  authors  call  those 

^  We  are  not  taking  here  into  consideration  the  question  of  the 
inheritance  of  the  effects  of  wounds  and  mutilations.  They  are  in- 
herited perhaps  exclusively  when  follozved  by  disease  as  Darwin 
said  (Variation,  II,  p.  57),  that  is  by  infection. 

^Alfred  Ploetz,  Die  Tiichtigkeit  unserer  Rasse  und  der  Schuta 
der  Schzvachcn,  1895,  p.  2)^.  See  also  p.  22,.  Also  Intracellularc  Pan- 
genesis, p.  29. 

^  G.  DuNCKER.  Die  Mefhodc  der  Variationsstatistik.  Roux's  Ar- 
chiv  f.  Entivick.  Mech.  d.  Org.,  Vol.  VIII,  i,  p.  115,  (1899). 


132  Controversial  Questions. 

characters  ''acquired"  which  can  be  traced  to  some  effect 
of  the  environment  on  the  organism  in  question.^ 

Acquired  characters,  as  the  term  is  understood  in 
Zoology  and  Anthropology,  are  parallel  to  the  so-called 
nutritional  modifications  of  the  botanist. 

Let  us  compare  the  two  groups  of  phenomena. 

We  often  find  in  the  literature  of  this  subject  a  dis- 
tinction drawn  between  the  so-called  nutritional  char- 
acters and  individual  variations.  The  former  are  said 
not  to  be  heritable  and  therefore  not  to  provide  material 
for  selection.  But  the  latter  are  assumed  to  be  due  to 
unknown  causes,  and  to  be  heritable  and  fixable  by  selec- 
tion. 

The  phenomena  of  nutritional  modifications  are 
equally  well  known  in  agriculture  and  in  horticulture. 
The  edges  of  the  field  and  the  spots  in  it  which  have  re- 
ceived an  undue  share  of  manure  give  rise  to  luxuriant 
plants.  On  the  other  hand  the  weed  that  germinates  in 
mid-summer  is  often  of  shrunken  stature  and  after  pro- 
ducing a  few  leaves,  blooms  and  sets  seed.  In  the  gar- 
den too,  plants  w^hich  are  grown  in  dry  places  or  in  poor 
soil  or  which  come  up  late  are  often  miserable  specimens. 
We  often  see  beside  richly  branched  Datura,  beside  Ama- 
r  ant  us  a  meter  high,  beside  normal  buckwheat  or  a  poppy 
covered  with  blossoms,  single  specimens  often  only  a 
decimeter  high,  almost  or  quite  unbranched,  with  small 
and  few  flowers  which  nevertheless  are  able  to  set  seed 
though  these  may  be  few  in  number. 

If  we  seek  for  the  grounds  on  which  the  distinction 
so  often  drawn  between  nutritional  modifications  and  in- 

^  Other  types  of  definition,  especially  those  which  involve  the 
question  as  to  whether  the  variations  arise  in  the  germ  or  not  lead 
to  much  confusion.  See  Intraccllulare  Pangenesis,  p.  206,  and  Kriiid- 
kundig  Jaarhoek,  Vol.  I,  1889,  p.  152. 


Acquired  Characters  and  Effects  of  Nutrition.  133 

dividual  variations  is  based,  we  seldom  find  them  clearly 
stated.  And  when  we  can,  they  usually  consist  in  some 
misapprehension  of  the  meaning  of  the  term  Heredity. 
Nutritional  modifications  are  deviations  of  considerable 
magnitude,  which  are  soon  lost  in  succeeding  generations 
in  accordance  with  the  law  of  regression.  They  do  in- 
deed bear  a  certain  resemblance  to  spontaneous  varia- 
tions or  sports  which  are  of  course  inherited.  It  is  per- 
haps on  some  such  train  of  thought  as  this  that  the  view 
that  they  are  not  inherited  may  rest. 

Ordinarv  variation  evidentlv  must  be  due  to  some 
cause  and  this  must  be  sought  for,  in  the  last  instance, 
in  the  environment :  that  is  in  nutrition,  using  that  term 
in  its  widest  signification. 

My  experiments  lead  me  to  the  conclusion  that  nutri- 
tional modifications  and  ordinarv  variations  are  one  and 
the  same  thing.  Great  changes  in  nutrition  result  in 
great  changes  in  the  plant  followed  by  a  proportionately 
speedy  regression.  And  as  the  change  in  the  organism 
does  not  become  independent  of  nutrition,  a  change  in 
the  amount  of  manure  in  the  next  generation  w^ill  affect 
the  plant  accordingly. 

Nutrition  in  the  widest  sense — the  conditions  of  life 
one  might  almost  say — is  at  the  bottom  of  all  individual 
variability.^  Every  character  varies  only  in  a  plus  or  luiiius 
direction.  Favorable  conditions  are  responsible  for  the 
former,  unfavorable  ones  for  the  latter.  Which  partic- 
ular influences  are  favorable  and  which  are  not,  is  of 
no  importance;  in  the  words  of  Knight:  "Superfluity 
of  nutriment  is  the  most  important  cause  of  variabihty: 
the  kind  of  nutriment  does  not  matter,"  he  said.     Future 

^  L'Unitc  dans  la  variation;  Revue  de  TUniversite  de  Bruxelles, 
III,  1898. 


134  Controversial  Questions. 

investigation  may  succeed  in  isolating  the  individual 
factors  of  the  environment  as  they  affect  the  organism, 
but  at  present  we  must  be  content  with  treating  them  to- 
gether, as  one  plienomenon. 

It  is  simply  impossible  to  draw  any  distinction  be- 
tween these  nutritional  modifications  and  individual  varia- 
tions in  the  strictest  sense  of  the  term.  There  seems  to 
be  every  stage  in  the  transition  from  a  state  of  affairs 
in  which  the  effect  of  external  conditions  is  easily  trace- 
able as  in  the  case  of  nutritional  modifications,  to  one  in 
which  the  very  reverse  is  the  case.  But  this  condition 
of  things  is  only  apparent,  for  the  more  closely  we  go 
into  the  matter  the  more  evident  does  it  become  that  the 
changes  of  this  kind  (individual  variations)  are  corre- 
lated with  changes  in  the  environment. 

In  horticulture  it  is  well  known  that  favorable  and 
highly  altered  conditions  lead  to  the  accumulation  and 
multiplication  of  individual  differences  whilst  ordinary 
and  uniform  conditions  tend  to  dissipate  them  and  to  re- 
duce all  the  individuals  to  the  same  level. ^ 

It  is  also  well  known  that  weedy  specimens  by  no 
means  lack  the  characters  of  the  variety  to  which  they 
belong  but  that  they  are  simply  nnnus-y 3.vmnts  in  fluc- 
tuating variability. 

More  accurate  investigation  will,  doubtless,  bring  out 
the  identity  of  true  individual  variations  with  nutritional 
modifications.  Mac  Leod  has  conducted  some  very  in- 
structive experiments  in  this  connection.  He  compared 
the  number  of  marginal  florets  on  well-grown  and  starved 
specimens  of  the  common  cornflower  (Centaurea  Cyaniis) 
and  found  that  there  was  a  very  high  positive  correlation 
between  number  and  vigor.     The  stronger  the  plant  the 

'  Intracellulare  Pangenesis,  p.  30. 


On  the  Inheritance  of  Acquired  Characters.     135 

richer  are  its  inflorescences  in  marginal  florets.  But  the 
luxuriance  of  the  plant  is  the  direct  result  of  nutrition, 
and  we  cannot  escape  the  conclusion  that  the  same  is  true 
of  the  marginal  florets.  And  the  same  rule  applies  to  the 
whole  organization  of  the  plant. -^ 

Our  conclusion  is  therefore  that  we  have  two  cat- 
egories of  characters,  one  which  includes  mutations  only ; 
and  another  which  includes  "acquired  characters,"  nu- 
tritional modifications  and  individual  variations.  The 
only  difference  between  true  individual  variations  and 
these  modifications  is  that  the  latter  are  determined  in  a 
more  evident  manner  bv  external  conditions. 


§  i6.  ON  THE  INHERITANCE  OF  ACQUIRED  CHAR- 
ACTERS. 

Herbert  Spencer  is  more  than  any  one  else  re- 
sponsible for  the  doctrine  of  acquired  characters."  He 
starts  with  the  belief,  based  on  general  observation,  that 
the  differences  between  the  individuals  of  a  species  are 
caused  by  the  conditions  in  which  they  live  and  that 
such  dift'erences  are  inherited. 

We  have  seen  in  the  preceding  sections  how  ac- 
quired characters  manifest  themselves  as  individual  devi- 
ations from  the  mean  character  of  the  type  in  question. 
The  question  of  their  inheritance  must  therefore  be 
judged  from  this  point  of  view. 

The  inheritance  of  individual  variations  differs  from 
that  of  mutations  in  that  the  former  exhibits  the  phe- 
nomena of  regression  and  of  accumulation  by  selection. 

^  J.  Mac  Leod,  Over  de  veranderlykheid  van  hcf  aantal  rand- 
bloemen  by  de  Korenbloem.  Handelingen  Vlaam.sch  Natuiirk.  Con- 
gres,  1899. 

"  See  especially  his  various  essays  in  The  Contemporary  Review. 


136  Controversial  Questions. 

Mutations  are  inherited  and,  as  a  rule,  constant  from 
the  time  when  they  appear.  Reversions  to  the  parent 
form  are  not  wanting;  but  they  are  very  rare  and  take 
place  as  sports  and  not  by  a  series  of  transitional  forms. 
We  call  this  atavism. 

The  inheritance  of  variations  or  deviations  from  the 
mean  of  the  type  is  quite  a  different  thing.  The  children 
deviate  less,  on  the  average,  from  tlie  mean  than  the 
parents  do;  on  the  other  hand  some  individuals  of  them 
mav  differ  more,  and  these  enable  us  to  increase  the 
deviation  by  means  of  selection. 

The  answer  to  the  question  whether  acquired  char- 
acters are  inlierited,  is  that  they  are  not  so  in  their  en- 
tirety, but  with  a  reduction  the  amount  of  which  is  in- 
dicated by  Galton's  law.  On  the  other  hand  the  gradual 
change  in  the  mean  character  of  a  race  which  can  be 
effected  by  selection  is  sufficient  proof  that  these  char- 
acters really  are  inherited.  The  question  whether  such 
variations  are  inherited  becomes  the  question  whether 
they  can  be  increased  by  selection.  And  as  far  as  I  am 
aware  no  investigations  have  been  made  which  prove 
that  this  cannot  be  done. 

The  so-called  innate  characters  as  opposed  to  acquired 
ones  are  believed  to  be  inherited  while  the  latter  are  not ; 
but  it  is  obvious  that  they  are  merely  inherited  devia- 
tions from  tiie  mean,  and  that  the  ancestors,  which 
showed  these  deviations  must  have  acquired  them  them- 
selves under  the  influence  of  external  conditions.  It 
would  lead  us  too  far  to  follow  up  this  line  of  thought 
although  such  a  discussion  would  undoubtedly  contribute 
to  the  ultimate  solution  of  this  question. 

If  we  regard  individual  variations  as  brought  about 
by  environment  and  by  nutrition   in  the  widest   sense, 


On  the  Inheritance  of  Acquired  Characters.     137 

we  arrive  at  the  conclusion  that  selection  consists  in  the 
choice  of  the  most  highly  nourished.^  Nutrition  can 
obviously  not  effect  the  full  amount  of  change  to  which 
it  may  lead,  in  a  single  generation.  Seeds  ripen  on  the 
mother-plant;  and  in  the  ripening  seed  the  young  plant 
passes  a  very  important  and,  what  is  still  more  important, 
a  very  sensitive  portion  of  its  life-history.  At  this  period 
it  is  obviously  dependent  on  the  nutritional  conditions 
of  the  mother.  If  the  mother-plant  is  not  strong — and 
not  grown  itself  from  strong  seed — it  cannot  give  rise 
to  the  strongest  offspring.  It  takes,  therefore,  a  few 
generations  for  the  surrounding  conditions  to  exert  their 
full  effect.  And  as  variations  are  caused  by  nutrition,  so 
it  must  be  possible  to  increase  them  by  selection  of  the 
best  nourished  individuals  within  some  few  generations. - 

It  has  been  my  object  in  this  discussion  to  offer  a  so- 
lution of  the  question  of  the  inheritance  of  acquired 
characters  b}^  a  critical  analysis  of  the  theory  of  selec- 
tion. A  solution  on  some  such  lines  as  those  suggested 
may  moreover  lead  us  to  the  only  path  that  will  help  us 
— that  of  experimental  investigation.  Once  on  this  path 
the  first  thing  we  have  to  do  is  to  find  out  whether  varia- 
tions which  are  to  a  great  extent  dependent  on  environ- 
ment can  be  intensified  or  diminished  by  selection  in  the 
ordinary  way. 

In  conclusion,  seeing  that  the  material  proof  is 
meagre,  we  may  illustrate  this  by  the  case  of  polycephaly 
in  Papaver  somniferum.^ 


^  It  seems  not  unreasonable  to  regard  the  effects  of  use  as  due  to 
the  mcreased  nourishment  of  an  organ. 

L'Unife  dans  la  variation,  pp.  21-22.     (Revue  de  TUniversite  de 
Bruxelles,  Tome  III,  1898,  Avril. 

^  AUmentatinn  et  selection.  Volume  jubilaire  de  la  Societe  de 
Biologic.  Paris  27  Dec.  1899,  p.  17.  Ref.  in  Biolog.  Centraiblatt, 
Bd.  XX,  No.  6,  1900. 


138 


Controversial  Questions. 


This  species  is  said  to  be  highly  variable;  but  all  that 
is  meant  by  this  is  that  it  is  very  rich  in  subspecies.  One 
of  these  is  distinguished  by  the  conversion  of  the  inner 
stamens  into  carpels.  It  is  cultivated  in  many  of  our 
gardens  under  the  name  of  P.  s.  monstruosiwi  or  P.  s. 
polycephalum  (Fig.  27).  It  is,  according  to  my  obser- 
vations always  true  to  its  type  but  is  highly  variable 
(Fig.  28).  The  number  of  supernumerary  carpels  may 
reach  1 50  or  more ;  or  they  may  be  reduced  to  mere  rudi- 
ments :  though,  so  far  as  my  experience  goes,  they  are 
never  entirely  lacking. 


Fig.  27.  Papaver  sommferum  polycephalum  s.  mon- 
sfrosiun,  with  a  whole  wreath  of  supplementary 
carpels.     From  above  and  from  the  side. 

The  variability  of  the  character  in  question  is  almost 
entirely  dependent  on  the  conditions  of  life.  From  the 
seeds  of  fruits  with  a  beautiful  circlet  of  carpels  we  can 
raise  a  good  harvest  of  such;  or  a  bad  one,  just  as  we 
please.  The  more  favorable  the  conditions  the  more 
numerous  the  supernumerary  carpels. 

It  is  evident  that  it  is  impossible  to  make  the  condi- 
tions for  each  plant  in  a  bed  exactly  similar,  for  when  the 
seed  first  begins  to  germinate  there  are  dififerences  in 
illumination,  humidity,  supply  of  nutriment,  etc.,  whose 
influences  tend,  as  growth  proceeds,  not  to  level  up  the 
differences,  but,  on  the  contrary,  to  accentuate  them.    In 


On  the  Inheritance  of  Acquired  Characters.     139 


experiments,  therefore,  only  the  mean  characters  of  (hf- 
ferent  beds  may  be  compared.  In  doing  so,  we  find  as 
a  general  rule  that  good  soil,  heavy  manuring,  a  sunny 
position,  evenly  distributed  moisture  and,  al)ove  all,  plenty 
of  room  between  the  plants,  tend  to  increase  the  numl)er 
of   carpels   per   flower;   whilst   sandy   soil,    shade,   cold. 


Fig.  28.  Papaver  somniferiim  polycephalum,  with 
slight  mukipHcation  of  carpels,  i  with  rudimen- 
tary carpels ;  2-4  with  i,  2  or  a  few  such  ;  5,  6  and 
7,  various  stages  in  the  fusion  of  the  lateral  fruits 
which  in  7  have  fused  to  a  split  wreath  round  the 
central  capsule  (which  has  been  removed).  8, 
stigma  of  the  central  fruit  seen  from  above. 

drought  and  crowding  of  the  plants  decrease  the  number 
to  a  very  considerable  extent ;  indeed  the  strongest  plants 
bear  a  full  "crown,"  the  feeblest  scarcely  any  trace  of  tlie 
monstrosity. 

In  the  process  of  looking  for  the  best  plants  for  ex- 
periment I  soon  noticed  that  the  individual  strength  of 


140  Controversial  Questions. 

the  plant  is  highly  correlated  with  the  number  of  super- 
numeraiy  carpels.  The  thickness  of  the  stem,  the  height 
of  the  plant,  but  especially  the  weight  of  the  fruit  afford 
a  good  index  of  strength.  If  we  arrange  the  individual 
plants  of  a  bed,  in  a  row  according  to  this  latter  character, 
we  find  that  they  form  an  almost  regularly  ascending 
series  with  regard  to  the  monstrosity. 

It  follows  therefore  that  a  selection  with  reference 
to  the  elaboration  of  the  carpellary  crown  is  by  no  man- 
ner of  means  without  relation  to  the  general  nutritional 
condition  of  the  plant.  On  the  contrary  such  a  selection 
is  merely  a  selection  of  the  most  highly  nourished. 

It  is  just  the  same  if  we  deal  with  the  //n'n //^-varia- 
tions. It  is  only  the  feeblest  specimens  which  are  desti- 
tute of  fully  developed  supernumerary  carpels  though 
as  we  have  said  they  possess  1  or  2  rudimentary  ones ; 
their  capsules  are  often  so  small  that  they  do  not  contain 
good  seed.  If  we  look  for  capsules  with  better  seeds  we 
find  more  pronounced  traces  of  the  monstrosity.  Retro- 
grade selection  or  selection  in  a  minus  direction  obviously 
consists  therefore  in  a  choice  of  the  weakest  individuals. 

Nevertheless,  in  both  these  cases  selection  has  the 
effect  that  it  usually  has.  From  the  seeds  of  self-fer- 
tilized plants  with  a  very  large  number  of  metamorphosed 
stamens  we  get  offspring  with  this  character  highly  de- 
veloped; from  seeds  from  fruits  poor  in  supernumerary 
carpels,  a  race  exhibiting  this  monstrosity  only  to  a  very 
slight  extent.  Continued  selection  for  a  few  generations 
intensifies  this  effect,  provided  that  the  conditions  under 
which  the  plants  were  grown  are  average  ones  and  that 
the  experiments  are  carried  out  on  a  large  scale  extend- 
ing over  several  square  meters  of  ground. 

External   conditions,    then,    exert   corresponding   in- 


On  the  Inheritance  of  Acquired  Characters.     141 

fluence  on  the  monstrosity  whether  we  have  regard  to 
the  carpels  themselves  or  to  the  seed  which  they  contain. 
In  the  experiments  in  question  their  operation  begins 
with  the  germination  of  the  seeds  which  are  to  produce 
the  plants  for  the  experiment.  The  degree  of  develop- 
ment of  the  monstrosity  in  such  cases  would  be  called 
an  acquired  character  in  the  usual  acceptance  of  the 
term.  There  is  no  obvious  reason  why  we  should  not 
apply  this  term  to  the  improved  value  of  the  seeds  ob- 
tained in  this  experiment — an  improvement  that  has  been 
brought  about  by  the  very  same  external  conditions 
which  affected  the  monstrosity. 

The  parallel  between  individual  strength  and  the  de- 
velopment of  the  monstrosity  is  not  absolute.  On  the 
contrary  there  is  a  very  simple  means  of  separating  the 
tw^o  and  of  obtaining  plants  of  great  vigor  but  almost 
destitute  of  supernumerary  carpels.  This  process  rests 
on  an  accurate  determination  of  what  we  may  call  the 
impressionable  period  in  the  development  of  the  mon- 
strosity. If  we  examine  the  young  buds  under  the  micro- 
scope at  intervals,  we  find  at  about  the  sixth  week  from 
the  germination  of  the  seed  the  stamens  and  supernumer- 
ary carpels  represented  by  small  protuberances  on  the 
growing  summit.  The  relative  number  of  the  two  struc- 
tures is  obviously  settled  at  this  stage;  all  attempts  to 
alter  their  relative  proportions  by  subjecting  them  to 
different  conditions,  after  this  stage  has  been  reached, 
have  been  without  avail.  The  critical  stage  occurs,  then, 
during  the  first  few  weeks  of  life ;  so  that  it  is  during  this 
period  alone,  if  ever,  that  it  should  be  possible  to  sup- 
press or  at  any  rate  to  reduce  the  monstrosity.  I  have 
succeeded  in  doing  this,  simply  by  transplanting  the 
young  seedlings  at  the  proper  time,  that  is  when  they 


142  Controversial  Questions. 

have  2  or  3  leaves  in  addition  to  the  cotyledons.  If, 
after  that,  I  make  the  conditions  as  favorable  as  possible, 
I  get  large  and  vigorous  plants  with  but  few  stamens 
transformed  into  carpels. 

By  this  device  therefore  it  is  possible  to  separate  the 
two  acquired  characters,  previously  associated.  The  ac- 
quisition of  the  visible  monstrosity  is  prevented ;  but  the 
seeds  attain  their  full  development. 

Parallel  experiments  with  other  species  and  other 
characters  have  convinced  me  that  we  are  dealing  in  this 
case  with  a  universal  and  very  important  principle.  I 
mean  the  simultaneous  influence  of  the  conditions  of  life 
on  the  visible  character  of  an  organism  and  on  its  germ 
cells.  In  other  words  (using  the  word  nutrition  in  its 
old  broad  sense)  we  may  say  that  selection  is  the  choice 
of  the  best  nourished  individuals. 

This  statement  can  only  be  taken  in  a  very  general 
sense;  for  there  are  individual  cases  to  which  it  does  not 
seem  to  apply,  as  for  instance  the  case  of  the  selection 
of  ^/znrz/.S'-variations.  Moreover  in  other  cases  there  are 
special  circumstances  which  prevent  its  exact  application, 
for  example  in  agricultural  selection  where  the  plants 
have  to  be  adapted  to  a  supply  of  manure  which  can  never 
be  copious.^ 

We  are  thus  led  to  see  that  a  proper  understanding 
of  the  difference  between  the  theories  of  Selection  and 
Mutation  opens  up  the  possibility  of  a  solution  of  the 
question  of  the  inheritance  of  acquired  characters.  Spe- 
cific characters  are  excluded  once  and  for  all  from  this 
discussion ;  they  arise  suddenly  by  mutation  and  are  not 
acquired.  Individual  deviations  from  the  mean  of  the 
specific  character  are  to  be  regarded  as  acquired  char- 

'  On  this  point  see  the  previous  chapter  especially  §  I2. 


Partial  Variability  and  Vegetative  Propagation.  143 

acters;  they  depend,  as  far  as  our  scanty  information 
goes,  almost  entirely  on  external  conditions;  which  in 
their  turn,  however,  need  some  generations  in  order 
to  exert  their  full  effect. 

The  only  way  to  decide  this  point  is  to  carry  out 
extensive  and  numerous  experiments  in  selection,  deal- 
ing with  the  general  significance  of  nutrition  in  its  widest 
sense. 

§    17.   ON    PARTIAL   VARIABILITY   AND    SELECTION    BY 
VEGETATIVE  METHODS   OF   PROPAGATION. 

Partial  variability,  that  is,  differences  in  homolo- 
gous organs  of  the  same  individual,  plays  a  much  more 
important  part  in  the  vegetable  than  in  the  animal  king- 
dom. It  is  as  universal  as  the  differences  between  in- 
dividuals and  is  usually  more  pronounced. 

It  conforms  to  exactly  the  same  statistical  laws.  -The 
size  of  leaves,  of  flowers  and  of  fruits,  the  number  of 
leaves  on  a  branch  and  of  the  parts  of  the  flower,  the 
rays  in  the  inflorescences  of  Umbelli ferae  and  Com- 
positae  even  if  determined  on  a  single  plant  can  be  tabu- 
lated by  means  of  frequency  curves.  The  phenomenon 
of  regression  in  partial  variability  has  been  made  the 
subject  of  special  study  by  Verschaffelt  :  and  the  laws 
describing  it  were  found  to  be  the  same  as  those  formu- 
lated by  Galton  for  individual  variability.^  Lastly,  the 
principles  of  selection  apply  to  these  phenomena  as  well 
as  to  individual  variability.^ 

This  great  similarity  between  individual  and  partial 

^  Ed.  Verschaffelt.  Galton's  "Rcs^ression  to  mediocrity"  by  on- 
^eslachtelyke  Voortplanting.  Livre  jubilaire  dedie  a  Charles  van 
Bambeke,  Bruxelles,  1899. 

^  See  the  end  of  this  section. 


144  Controversial  Questions. 

variability  serves  to  place  the  antithesis  between  muta- 
bility and  individual  variability  in  an  even  stronger  light. 

I  shall  therefore  briefly  touch  on  a  few  examples  of 
partial  variability. 

One  of  the  most  valuable  pieces  of  w^ork  in  biology 
are  Stahl's  classical  researches  on  the  effect  of  sunny 
and  shady  positions  on  the  development  of  foliage  leaves.^ 
The  insolated  leaves  are  generally  smaller,  stouter,  poorer 
in  air  spaces  and  richer  in  chlorophyll  and  have  stronger 
veins;  they  are  in  fact  adapted  to  turn  the  strong  sun- 
lio-ht  to  best  account.  The  shaded  leaves  are  broader  and 
thinner,  with  larger  air  spaces  and  delicate  epidermis — 
in  fact  eminently  adapted  to  make  the  most  of  the  meagre 
supply  of  light  at  their  disposal.  Lactuca,  Iris,  Fagus 
are  the  best  known  examples.  The  more  a  species  has 
become  specialized  as  a  ''sun-plant"  as  Pinus,  or  a  ''shade- 
plant"  as  Chclidoiiium,  the  less  is  its  power  of  adaptation 
in  this  direction. 

Still  more  important,  if  possible,  than  Stahl^s  re- 
searches are  Gaston  Bonnier's  recent  investigations  on 
the  adaptation  of  plants  to  arctic  and  alpine  climates.- 
Both  authors  dealt  with  partial  variability;  the  former 
dealing  with  the  problem  from  a  comparative  standpoint, 
the  latter  from  an  experimental  one.  In  Bonnier's  ex- 
periments a  single  individual  of  each  species  that  was 
dealt  with  was  divided  into  two.  One  of  the  parts  was 
then  grown  on  the  Alps  or  Pyrenees ;  the  other  on  low 
lying  land.    In  the  course  of  a  very  short  time  the  former 

^  Jenaische  Zeitschrift  fur  Naturw.,  XVI,  N.  F.,  IX,  i,  2,  1883. 

^G.  Bonnier.  Rccherches  expcrimcntalcs  siir  Vadaptation  dcs 
plantcs  au  cUmat  alpin.  Ann.  Sci.  nat.  7.  Serie,  T.  20.  Lcs  plantes 
arctiqucs  coinparccs  aux  mhnes  cspcccs  dcs  Alpes  ef  des  Pyrenees. 
Revue  generale  de  Botanique,  Tome  6;  Influence  de  la  lumicre  elec- 
triqiie  sur  la  forme  ct  la  structure  des  plantes.     Ibid.,  T.  7,  1896. 


Partial  Variability  and  Vegetative  Propagation.  145 

half  took  on  the  famihar  dwarf  habit  of  alpine  plants 
while  the  latter  soon  exhibited  the  general  features  of 
lowland  plants.  The  leaves  of  alpine  plants  are  smaller, 
thicker,  firmer  and  more  compact  in  build,  poorer  in  air 
spaces,  richer  in  chlorophyll  and  dark  green;  in  a  given 
period  of  time  they  assimilate  more  carbonic  acid  gas 
than  the  corresponding  parts  of  plants  grown  in  the  plain. 
They  are  perfectly  adapted  to  the  bright  light  and  the 
short  summer  of  the  Alps ;  in  the  space  of  a  few  weeks 
they  have  to  store  up  nourishment  for  the  wdiole  year. 
The  underground  stem  of  an  alpine  plant  is  well  devel- 
oped and  richly  branched ;  the  exposed  parts  are  on  the 
other  hand  short  and  consist  of  few  and  stunted  inter- 
nodes;  it  has  large  flowers  and  so  forth.  In  all  these  re- 
spects the  half -specimens  transplanted  to  the  Alps  as- 
sumed the  characters  of  normal  alpine  plants. 

Arctic  plants  exhibit  a  corresponding  adaptation ;  the 
climate  is  of  course  cold,  but  the  air  is  damp,  and  this 
affects  the  anatomical  structure  of  the  leaves.  This  case 
of  partial  variability  has  also  been  investigated  by  Bon- 
nier, and  with  analogous  results. 

I  have  carried  out  similar  experiments,  on  a  Crassula- 
like  composite  Othonna  crassifolia^  It  is  a  South  Afri- 
can plant  with  almost  cylindrical  fleshy  leaves  pointed  at 
the  end.  The  development  of  these  leaves  is  to  a  great 
extent  dependent  on  the  dampness  of  the  air  and  the 
ground.  Grown  in  damp  soil,  the  Othonna  is  dark  green, 
with  long  leaves,  it  is  richly  branched  and  of  very  luxuri- 
ant growth;  grown  in  dry  soil  on  the  other  hand  it  is 
very  pale  green,  with  short  globose  leaves,  and  hardly 
branched  at  all.  They  also  exhibit  a  dependence  on  ex- 
ternal conditions  in  the  number  of  their  ray-florets,  a 

^  Kruidk.  Jaarbock  Dodonaea.     Bd.  XII,  1900,  Taf.  i. 


146 


Controversial  Oucstions. 


character  which  has  so  often  afforded  material  for  sta- 
tistical investigation.  Their  variation  can  be  expressed 
in  the  form  of  curves ;  the  mean  for  dark  green  individ- 
uals which  have  been  liberally  watered  stands  at  13  ray- 
florets,  but  for  a  separate  part  of  the  same  plant  which 
had  been  kept  relatively  dry  the  mean  was  12. 


Fig.  29.  Helianthemum  vulgar e  after  G.  Bonnier  {loc.  cit., 
Plate  20).  The  plant  was  divided  in  two  halves  of  which 
one  (a)  was  subsequently  cultivated  in  the  plain  and  the 
other  (b)  in  the  Alps.  Both  halves  are  reduced  on  the 
same  scale  in  the  figure. 

In  these  instances  nutritional  modifications  are  seen 
to  be  adaptive  characters ;  in  one  case  these  adaptive 
differences  are  what  we  should  describe  as  instances  of 
normal  A'ariability ;  and  they  are  obviously  brought  about 


Partial  Variability  and  Vegetative  Propagatiun.  147 


by  the  same  causes.     This  alone  would  suffice  to  show 
how  intimately  the  two  phenomena  are  connected. 

A  further  fact,  to  which  much  too  little  attention  has 
been  paid,  is  the  gradual  accumulation  of  some  peculiarity 
by  means  of  selection  of  a  character  in  a  plant  propagated 


Figs.  30  and  31. 

Othonna  carnosa,  la  grown  in  moist  earth  and  16  in  dry; 
the  former  with  long  leaves  forming  no  rosettes  and  very 
strong;  the  latter  covered  with  rosettes  of  short  stout  thick- 
leaves.^ 

Othonna  crassifolia.  Ila  grown  in  damp  soil  and  116  in  dry, 
lie  a  flower,  lb  and  116  were  branches  hanging  over  the 
edge  of  the  pot. 

by  vegetative  methods.     An  example  of  this  has  been 
given  by  Darwin  :^ 

The  well-known  English  plant-breeder  Salter  ef- 
fected a  considerable  improvement  in  certain  variegated 

'  Othonna  carnosa  is  very  like  O.  crassifolia,  but  has  consider- 
ably larger  leaves  and  somewhat  larger  flowers.  But  its  relation  fo 
damp  air  and  so  forth  is  the  same  as  that  of  O.  crassifolia. 

^  J  Variations  of  Ajiimals  and  Plants,  I,  p.  443,  444. 


148  Controversial  Questions. 

plants  by  carefully  selecting  the  twigs  which  were  to  be 
used  as  cuttings.  His  plan  was  to  look  over  a  plant  for 
any  leaves  which  showed  even  the  slightest  indication  of 
variegation  and  then  to  make  cuttings  from  the  buds  in 
the  axils  of  these  leaves.  The  leaves  gave  the  promise 
of  a  higher  degree  of  variegation,  and  justified  it  by  en- 
abling Salter  to  put  several  varieties  on  the  market. 

The  same  principle  has  recently  been  applied  with  the 
most  satisfactory  results  by  J.  Kobus  in  the  cultivation 
of  sugar  cane  in  Java.^  There  are  great  difficulties  in 
the  way  of  propagating  the  selected  plants  sexually  in 
this  case,  the  most  serious  of  which  is  that  the  best  kind 
of  all — the  Cheribon  cane — is  sterile.  Kobus,  therefore, 
sought  among  the  best  varieties  that  which  was  richest 
in  sugar  and  only  used  this  to  take  cuttings  from  (such 
cuttings  are  called  bibif  in  Java).  But  all  the  specimens 
of  a  single  variety  are,  in  this  case,  obtained  by  vege- 
tative methods,  so  that  every  variety  is,  as  we  have  ex- 
plained above  (pp.  84-85)  a  single  individual.  The  cut- 
tings from  individuals  rich  in  sugar  give  rise  to  rich 
canes.  This  method  insures,  in  the  first  place,  the  elimi- 
nation of  the  less  valuable  plants  in  a  very  simple  and 
effective  manner,  and  in  the  second,  the  use  of  the  very 
best  canes  as  breeding  material :  moreover  the  yield  is 
much  more  quickly  and  much  more  simply  increased 
than  by  the  ordinary  method  of  selection. 

To  sum  up :  I  claim  that  I  have  shown  that  there  is 
a  complete  parallel  between  partial  and  individual  varia- 
bility; and  that  both  are  brought  about  by  the  same 
causes.  These  are  external ;  they  are  to  be  found  in  the 
amount  of  light  and  of  moisture  and  in  such  other  fac- 
tors as  would  be  placed  in  the  category  of  "nutritional" 

^  ArcJiief  voor  lava-Suikerindusfric,  1898,  Nr.  16,  1899,  Nr.  15-16. 


Variation  and  Adaptation.  149 

— according  to  the  old  acceptance  of  the  term  nutrition. 
Their  effect  can  be  intensified,  in  the  case  of  partial  as 
well  as  in  that  of  individual  variability,  in  the  course  of 
a  few  generations  whether  these  be  sexually  or  vegeta- 
tively  produced. 


§     i8.    VARIATION    AND    ADAPTATION. 

It  has  often  been  maintained  that  groups  of  individ- 
uals which  vary  are  better  adapted  to  a  changing  environ- 
ment than  groups  of  individuals  which  are  all  alike. 

Variability  must  not,  however,  in  my  opinion  be  re- 
garded solely  as  an  adaptation.  But  the  fact  that  the 
amplitude  of  variation,  the  Abdnderungsspielrauni  as 
Ammon  has  happily  termed  it,-^  is  very  different  in  dif- 
ferent organs  and  characters  and  also  in  different  species 
of  animals  and  plants  suggests  that  there  must  be  a 
definite  cause  for  it  in  each  particular  case. 

The  form  of  a  Ouetelet^s  curve  is  determmed  by 
two  factors;  the  magnitude  of  the  mean  value  and  the 
amplitude  of  variation.  We  are  accustomed  to  regard 
as  a  measure  of  the  latter  that  part  on  the  base  line 
which  includes  half  of  the  individuals  between  the  mean 
and  the  furthest  scale  character.  The  mean  (M)  and  the 
amplitude  (O)  are  independent  values.  But  they  are 
both  specific  characters  at  least  in  every  case  in  which 
they  deviate  from  the  normal.  And  it  is  not  necessary  to 
say  here  that  specific  characters  are  at  least  in  very  many 
instances  adaptive  characters. 

I  shall  now  examine  two  very  important  phenometia 
from  this  point  of  view.     First,  the  frequently  enormous 

^  Otto  Ammon,  Dcr  Ah'dnderungsspielraum.  Naturwissensch. 
Wochenschrift,  1896,  Nos.  12-14. 


150  Controversial  Questions. 

variability  of  vegetative  organs  and  the  equally  remark- 
able uniformity  of  organs  connected  with  reproduction; 
and  further  the  dissimilarity  between  seeds  on  one  and 
the  same  plant. 

Vegetative  organs  are  as  a  rule  much  more  variable 
than  those  which  are  concerned  with  sexual  processes. 
The  characters  of  flowers  exhibit  very  slight  variability : 
and  the  more  they  are  adapted  to  the  visits  of  insects  the 
less  variable  are  they.  The  number  of  petals  and  stamens 
is  remarkably  constant  so  long  as  the  number  is  small; 
but  when  their  number  becomes  so  great  that  a  few  more 
or  less  would  exert  no  perceptible  influence  on  the  shape 
of  the  flower,  it  ceases  to  be  constant.  The  symmetry 
of  the  flower  is  hardly  subject  to  variation  at  all.  The 
more  exactly  a  flower  is  adapted  to  the  visits  of  single 
genera  or  species  of  insects  the  more  serious  would  any 
deviation  from  the  normal  form  be ;  and  we  do  as  a  mat- 
ter of  fact  find  that  in  such  cases  deviations  are  exceed- 
ingly minute  and  rare.  On  the  other  hand  when  we  con- 
sider the  vegetative  life  of  a  plant  we  see  that  it  is  of  the 
highest  importance  that  the  plant  should  be  able  to  make 
the  most  of  the  amount  of  light,  moisture,  inorganic 
food,  and  space  at  its  disposal,  that  is,  to  be  in  a  posi- 
tion to  develop  luxuriantly  in  favorable  circumstances 
and  economically  in  unfavorable  ones. 

There  is  a  whole  series  of  plants  which  are  remark- 
able for  an  extraordinary  plasticity  of  this  kind.  It  is 
often  assumed  that  the  general  conditions  affecting  the 
growth  of  a  plant  on  such  a  small  area  as  a  garden  bed 
are  in  themselves  uniform  or  at  any  rate  that  they  can 
be  easily  made  so.  But  my  experience,  which  is  derived 
from  such  experiments  extending  over  more  than  ten 
years,  has  convinced  me  that  the  difliculties  in  the  way  of 


Variation  and  Adaptation.  151 

insuring  such  uniformity  are  almost  insuperable.  And 
if  tliese  differences  cannot  be  removed  in  our  experiments 
it  is  obvious  that  the  eft'ect  they  have  in  nature  must  be 
considerable.  So  that  a  sowing  of  dissimilar  seeds  in 
nature  gives  more  promise  of  a  strong  generation  than 
a  sowing  of  similar  seeds.  For  the  conditions  obtaining 
in  the  different  parts  of  a  circumscribed  area,  as  far  as 
they  affect  the  germination  and  growth  of  a  seed  are  very 
dift'erent,  partly  on  account  of  differences  in  dampness 
and  fertility — which  varies  inversely  with  the  degree  of 
exhaustion  of  the  soil — partly  on  account  of  enemies  in 
the  shape  of  animals  and  partly  on  account  of  competitors 
in  the  shape  of  plants  between  which  they  happen  to  be 
lodged.  But  if  the  number  of  seeds  is  great  and  the 
differences  between  them  are  considerable,  there  is  every 
likelihood  that  at  any  rate  some  of  them  will  find  a  situa- 
tion which  suits  them. 

Let  us  take  a  particular  case  and  compare  the  varia- 
bility which  exists  in  nature  with  that  which  is  exhibited 
by  a  population  produced  by  sowing  the  seeds  of  a  single 
plant.  I  have  chosen  as  an  example  the  yellow  corn- 
flower of  our  fields  (Chrysanthemum segetum)  and  have 
paid  attention  to  the  number  of  ray-florets  on  the  inflor- 
escence.-^ The  average  number  of  these  is  13;  but  the 
plants  vary  round  this  value  in  the  one  direction  to  6,  in 
the  other  to  21. 

Dr.  H.  W.  Heinsius  has  been  kind  enough  to  make 
some  observations  for  me  in  the  field  in  North  Brabant 
in  the  Netherlands;  they  involved  the  counting  of  ray- 
florets  on  325  flowers.  In  1894  I  sowed  the  seeds  of  a 
13-rayed  plant  and  counted  the  ray-florets  of  the   first 

^  Ueher  Curvcnselection  hei  Chrysanthemum  segetum,  Berichte 
d.  d.  Bot.  Ges.,  1899,  XVII,  pp.  87-89.  The  numbers  given  there  are 
here  reckoned  as  percentages. 


152  Controversial  Questions. 

flower  on  every  plant  in  the  population  obtained.  There 
were  338  plants.  Both  series  of  numbers  are  transmuted 
into  percentages  to  make  their  comparison  simpler.  Here 
is  the  result : 


/\. 


€    7   a   3   10  Tt   13  13  n  IS  ts  n  w  19  »fli  zi 

Fig.  2>^.  Curves  of  large  and 
small  amplitude.  A,  curve 
of  the  variability  of  the 
number  of  ray-florets  of 
ClivysantJiemmn  segetum 
growing  wild.  B,  the  same 
curve  describing  a  crop  ob- 
tained in  1894  by  sowing  the 
seeds  of  a  13-rayed  plant. 
The  numbers  at  the  feet  of 
the  ordinates  correspond  to 
the  number  of  ray-florets  in 
the  inflorescence. 


NUMBER 

IN  THE 

AFTER 

OF  RAYS 

OPEN 

SELECTION 

6 

0.3 

0.0 

7 

0.3 

0.0 

8 

6.8 

0.0 

9 

4-3 

0.3 

10 

3-1 

0.9 

II 

7-1 

2.3 

12 

9.9 

9-3 

13 

34-2 

65.3 

14 

14.2 

14.8 

15 

8.0 

^■Z 

16 

Z-7 

i-S 

17 

5-2 

1.2 

18 

0.9 

0.9 

19 

0.9 

0.3 

20 

0.9 

0.6 

21 

0.0 

0.3 

In  Fig.  32  these  two  series  of  figures  are  exhibited 
graphically  as  curves.  It  will  be  seen  at  once  that  the 
dotted  curve  which  describes  the  result  of  the  culture  in 
1894  has  a  much  higher  apex  and  is  much  steepe^r  than 
the  other;  that  is,  it  has  a  much  smaller  amplitude.  In 
other  words,  the  deviations  from  the  mean  in  plants 
growing  in  the  field  are  greater  in  size  and  number  than 
they  are  among  the  children  of  a  single  plant,  even  when 
this  plant  bore  exactly  the  mean  character  of  the  type. 

It  is  clear  that  a  generation  corresponding  to  curve 


Variation  and  Adaptation.  153 

A  will  have  less  difficulty  in  finding  conditions  to  suit 
it  than  a  less  variable  one,  such  as  might  be  described  by 
curve  B.  The  offspring  of  seeds  of  varying  parents  are 
therefore  at  a  considerable  advantage. 

And  now  we  come  to  the  significance  of  crossing. 
The  essence  of  fertilization  is  not  the  union  of  the  two 
sexes  but  the  mixture  of  the  heritable  characters  of  two 
individuals  with  a  different  past  or  at  any  rate  of  indi- 
viduals which  have  been  subjected  to  different  external 
conditions.  The  advantages  accruing  from  the  fusion 
of  different  variants  afford,  in  my  opinion,  a  fair  ex- 
planation of  the  existence  of  sexual  reproduction.^ 

Darwin's  well-known  aphorism :  nature  abhors  per- 
petual self-fertilization,  does  not  seem  to  me  to  express 
the  matter  quite  exactly.  It  is  not  sufficient  that  isolated 
crossings  should  occur  from  time  to  time ;  on  the  con- 
trary, it  is  necessary  that  a  certain  percentage  of  indi- 
viduals should  always  be  crossed.  For  in  this  way  varia- 
bility will  be  increased  ;^  but  the  point  is  not  that  its  range 
should  be  as  wide  as  possible  but  that  it  should  be  main- 
tained at  a  limit  which  the  environment  demands.^ 

The  degree  of  the  deviation  of  the  individual  is  al- 
ready determined  in  the  seed.  But  seeds  differ  among 
themselves  not  only  in  relation  to  the  characters  of  their 
parents,  but  according  to  the  position  on  the  plant  itself 
and  according  to  their  weight.  The  significance  of  these 
factors  and  their  bearing  on  variability  has  often  been 
the  subject  of  research ;  numerous  isolated  papers  on  this 
subject  exist  but  they  need  a  comparative  and  critical 

^  Intracelhdare  Pangenesis,  p.  29. 

^  A.  GiARD  in  Comptcs  rendus  de  la  Soc.  de  Biologie,  4  Nov.  1899, 
p.  2,  and  LiGNiER  in  Festschrift  su  Ehren  Giard's,  Nov.  1899. 

^  See  especially  Ammon,  Der  Ah'dnderungsspielraum,  loc.  cit., 
P-  53. 


154  Controversial  Questions. 

treatment.^  Far  too  little  attention  has  been  paid  to  the 
relation  between  the  range  of  variation  of  the  individual 
characters  and  the  degree  of  their  adaptation  to  changing 
conditions  of  life;  and  the  whole  matter  is  still  very  much 
of  a  mystery.  Here  again  it  is  probable  that  further 
study  will  tend  to  emphasize  the  fundamental  distinction 
between  variability  and  mutability. 

§   19.  VARIABILITY  IN  MAN,  AND   SOCIAL  QUESTIONS. 

A  noteworthy  feature  of  the  last  few  decades  has 
been  the  attempt  to  apply  the  results  of  evolutionary  in- 
vestigation to  the  solution  of  the  great  problems  of  hu- 
manity and  social  life.  Many  have  followed  along  the 
lines  which  the  great  English  philosopher  Herbert  Spen- 
cer laid  down ;  and  a  considerable  mass  of  literature  has 
accumulated  on  this  subject.  There  are  at  least  two  im- 
portant schools  in  this  field  of  research.  Otto  Ammon 
is  the  founder  of  one  of  them:  his  method  consisted  in 
the  application  of  the  results  of  statistical  investigations. 
The  other,  and  much  larger  school,  is  that  which  aims  at 
the  application  of  biological,  and  particularly  of  zoological 
knowledge  to  the  solution  of  social  problems. 

Ammgn^s  method  seems  to  me  to  be  justified  by  the 
fruit  it  has  borne;  but  the  writings  of  biologists  in  gen- 
eral and  zoologists  in  particular  seem  to  me  to  fall  short 
of  a  desirable  standard  of  lucidity  and  directness.- 

Many  mistakes  may  in  the  future  be  avoided  if  a  clear 

distinction  be  drawn  between  mutability  and  variability 

in  the  ordinary  sense. 

*  See  Von  Rumker,  Der  wirthschaftliche  Mehrwerth,  loc  cif., 
pp.  140-141. 

^  A  general  account  of  the  methods  and  results  of  this  school, 
and  a  bibliograph}-  will  be  found  in  O.  Hertwig's  essay,  Die  Lchre 
vom  Organismus  iitid  Hire  Beziehimg  zur  Sozialwissenschaft,  1899. 


Variability  in  Man,  and  Social  Questions.         155 

The  variability  exhibited  by  man  is  of  the  fluctuating 
kind :  whereas  species  arise  by  mutation.  The  two  phe- 
nomena are  fundamentally  different.^  The  assumption 
that  human  variability  bears  any  relation  to  the  variation 
which  has  or  is  supposed  to  have  caused  the  origin  of 
species  is  to  my  mind  absolutely  unjustified. 

Man  is  a  permanent  type,  like  the  vast  majority  of 
species  of  animals  and  plants.  The  laws  for  permanent 
types  apply  to  man ;  though  often  with  a  qualification. 
But  the  laws  which  describe  the  changes  by  which  indi- 
vidual permanent  types  arise  cannot  be  so  applied.  As 
we  have  seen  it  is  characteristic  of  these  types  to  exhibit 
a  certain  amount  of  fluctuating  variability.  Man  is  no 
exception  to  this  rule. 

Therefore  all  that  we  can  apply  to  the  treatment  of 
social  questions  is  our  knowledge  of  ordinary  variability. 
The  facts  of  specific  differentiation  are  interesting  but 
not  relevant. 

The  mental  qualities  of  the  human  race  are  closely 
bound  up  with  their  bodil}^  organization,  and  this  has 
been  shown  to  conform  to  the  same  laws  as  those  by 
which  we  describe  individual  variability  in  plants  and 
animals. 

Of  late  3^ears,  Kollmann  has  done  more  than  any 
one  else  to  insist  on  the  distinction  which  should  be 
made  between  persistent  racial  characters  and  fluctuating 
intra-racial  characters  in  the  case  of  man — a  distinction 
which  was  also  emphatically  maintained  by  Virchow.- 

Favorable  and  unfavorable  conditions  of  life,  migra- 

^L'Unite  dans  la  Variation,  loc.  cit.,  p.  17. 

^Kollmann,  Die  angebliche  Entstchung  netier  Rassentypen  in 
Correspondenzblatt  der  d.  Gesellsch.  fiir  Anthropologic,  Vol.  31,  No. 
I.  Jan.  1900.  p.  I.  A  bibliography  of  the  subject  will  be  found  on 
P'lge  5- 


156  Controversial  Questions. 

tion  to  a  different  climate  and  so  forth  affect  the  fluc- 
tuating cliaracters  of  man  to  no  small  extent.  But  only 
for  a  time;  as  soon  as  the  disturbing  factor  is  removed, 
the  effect  which  it  produced  disappears.  The  morpho- 
logical characters  of  the  race  on  the  other  hand  are  not 
in  the  least  affected  by  such  influences.  New  varieties 
do  not  arise  by  this  means.  Since  the  beginning  of  the 
diluvial  period  man  has  not  given  rise  to  any  new  races 
or  types.   He  is,  in  fact,  immutable,  albeit  highly  variable. 

In  order  to  attain  to  some  insight  into  the  causes  and 
significance  of  individual  differences  in  man  we  must 
study  the  corresponding  differences  which  are  presented 
by  an  assemblage  of  forms  belonging  to  a  single  species 
of  animal  or  plant.  Here  is  a  wide  and  fertile  field  open 
for  investigation ;  but  one  in  which  the  harvest  of  in- 
formation has  been  poor  so  far. 

Ammon,  as  we  have  already  said,  is  the  most  con- 
siderable of  the  anthropological  writers  on  this  subject. 
Although  he  does  not  distinguish  between  the  theories  of 
selection  and  mutation,  he  sees  clearly  that  our  knowl- 
edge of  the  origin  of  species  in  nature  has  no  bearing 
on  social  questions.  And  as  it  is  on  this  point  that  most 
sociological  writers  are  in  error  it  will  be  worth  our 
while  to  pa}^  some  attention  to  his  actual  position.^ 

Ammon  sets  forth  the  modern  theory  of  selection  in 
five  theses  of  which  the  first  four  deal  with  heredity, 
variability,  the  struggle  for  existence  and  elimination  of 
the  unfit  (Natiirliche  Auslese).^ 

The  fifth  thesis  deals  with  the  theory  of  descent.  It 
runs :  ''The  forms  and  characters  which,  having  arisen 

^  Otto  Ammon,  Die  Gcsellschaftsordnung  und  Hire  nafilrlichen 
Grundlagcn,  2d  edition,  1896,  pp.  9-10. 

^This  happy  phrase  of  Ammon  is  eminently  preferable  to  Natiir- 
liche Zuchtwahl. 


Variability  in  Man,  and  Social  Questions.         157 

as  the  result  of  variability,  are  favorable  to  the  survival 
of  the  individual  increase  in  relative  number  by  the  nat- 
ural elimination  of  unfa^vorable  ones.  New  varieties  and 
species  arise  by  the  gradual  accumulation,  generation  by 
generation,  of  the  favorable  deviations  from  the  original 
type. 

And  then  he  adds,  'The  substance  of  the  fifth  thesis 
is  often  challenged  on  the  ground  that  we  are  not  in  a 
position  to  state  that  deviations  from  a  certain  type  can 
lead  to  the  origin  of  a  new  species  by  the  elimination  of 
the  unfit.  Fortunately  we  need  not  wait  for  the  settle- 
ment of  this  controversy.  I  have  only  enunciated  the 
5th  thesis  in  order  to  give  a  complete  survey  of  Darwin's 
theory;  but  it  has  no  bearing  zvliatsoever  on  our  present 
socio-anthro polo gical  inquiry/' 

This  is  not  the  place  in  which  to  go  further  into  this 
question.  The  danger  of  the  application  of  the  theory 
of  descent  to  social  questions  has  already  been  pointed 
out  by  men  who  are  cjualified  to  express  an  opinion. 
Quite  lately  Karl  Pearson  has  severely  criticized  Ben- 
jamin Kidd's  book  on  social  evolution  which  is  often 
recommended  in  England  as  the  best  up-to-date  work 
on  the  subject.  If  the  reader  is  not  clear  as  to  what  is 
meant  by  the  dangers,  to  which  we  have  referred,  which 
attend  the  application  of  the  so-called  scientific  method 
to  the  treatment  of  these  problems  he  will  do  well  to 
read  this  critical  essay  carefully.-^ 

So  long  as  it  is  impossible  to  investigate  the  social 
qualities  of  man  directly  it  must  suffice  to  do  what  we 
can  by  analogy.  Material  for  this  argument  is  afforded 
by  the  study  of  variability  in  the  stricter  sense  of  the 

^  Karl  Pearson,  Socialism  and  Natural  Selection,  The  Fort- 
nightly Review,  1894. 


158  Controversial  Questions. 

term ;  but  our  knowledge  of  the  mode  of  the  origin  of 
species  will  not  help  us  in  this  investigation.^  The  study 
of  variability,  in  plants  and  animals,  as  well  as  in  the 
physical  characters  of  man  may  thus  serve  a  higher  pur- 
ix)se. 

It  is  singularly  fortunate,  in  the  present  state  of 
affairs,  that  these  analogies  should  be  limited  to  varia- 
bility as  opposed  to  mutability.  Variability  is  accessible 
to  investigation  from  many  points  of  view,  which  is  far 
from  being  the  case  with  mutability.  Many  principles 
in  variability  have  been  discovered  and  dealt  with  by 
OuETELET  and  Galton  and  their  followers :  the  methods 
of  this  school  can  be  partly  applied  directly  to  the  in- 
vestigation of  mental  characters  and  partly  effect  a  con- 
siderable simplification  of  treatment. 

There  lies  here  a  wide  and  fertile  field  of  investiga- 
tion, especially  for  botanists.-  One  of  the  most  impor- 
tant conditions  in  experiments  on  selection  is  the  num- 
ber of  individuals  in  each  generation ;  and  plants  readily 
lend  themselves  to  cultivation  by  hundreds  without  any 
of  the  ill  effects  which  usually  attend  overcrowding.  Such 
experiments  are  Avell-nigh  impossible  in  the  case  of  ani- 
mals :  and  out  of  the  question  in  the  case  of  man.  Here, 
as  in  many  other  spheres,  the  botanist  must  take  the  lead 
and  the  zoologist  and  anthropologist  will  follow  after- 
wards. 

Of  late  years  the  statistical  study  of  variability  has 
become  specialized  as  a  distinct  branch  of  science  thanks 
to  the  labors  of  Bateson  and  Weldon  among  zoologists, 
LuDWiG  among  botanists  and  Karl  Pearson  and  Dunc- 

^  See  also  H.  J.  Haycraft,  Darivinism  and  Race  Progress,  and 
further,  on  the  possibility  of  replacing  selection  by  improved  nutri- 
tion :  L'Unite  dans  la  Variation,  p.  21. 

'  L' Unite  dans  la  Variation,  loc.  cit.,  pp.  14-15. 


Some  Subjects  for  Future  Investigation.         159 

KER  among  mathematicians.  Botanical  work  in  this 
field,  has  also  been  done  by  Verschaffelt,  Burkill, 
Haake,  Davenport,  Blankinship,  Mac  Leod  and 
many  others.^ 

Let  us  summarize  the  foregoing  discussion.  The 
mental  and  moral  characters  of  men  exhibit  fluctuating 
variabihty.  The  laws  therefore  which  describe  this  phe- 
nomenon can  be  profitably  applied  to  such  characters. 
And  we  shall  have  to  be  contented  with  this  manner  of 
treating  the  subject  so  long  as  a  direct  investigation  by 
biometric  methods,  and  by  experiments  in  selection  are 
out  of  the  question.  The  foundations  of  sociolog}^  must 
be  furnished  by  biology.  And  we  may  hope  that  the 
time  is  not  far  distant  Avhen  a  fruitful  cooperation  be- 
tween these  two  sciences,  apparently  so  much  akin  but 
actually  so  far  apart,  may  be  brought  about. 

But  no  theory  of  the  origin  of  species  can  have  any 
bearing  at  all  on  this  subject. 


§  20.  SOME  SUBJECTS  FOR  FUTURE  INVESTIGATION. 

In  the  preceding  discussion  I  have  had  occasion  to 
draw  attention  not  merely  to  the  splendid  achievements 
of  my  predecessors  but  also  to  the  numerous  gaps  in  our 
knowledge. 

The  study  of  variability  as  opposed  to  mutability  is 
a  branch  of  human  knowledge  which  has  developed  witli 
great  rapidity  in  the  last  few  years.  The  statistical 
method  of  dealing  with  this  phenomenon  is,  as  we  have 

^  A  survey  of  the  literature  on  this  subject  has  been  given  by 
G.  DuNCKER,  Die  Methode  der  Variationsstatistik ;  Roux's  Archh' 
filr  Entzvickclnngsmechamk,  Vol.  VIII,  1899,  p.  167;  and  by  Oster- 
HOUT,  Problems  of  Heredity  in  Contributions  Bot.  Semin.  Univ. 
California    1898. 


160  Controversial  Questions. 

already  said,  firmly  established :  comparative  and  experi- 
mental methods  are  just  coming  on. 

I  propose,  therefore,  to  suggest  a  series  of  problems 
the  solution  of  which  would  in  my  opinion  throw  much 
light  on  the  essential  difference  between  mutability  and 
variability. 

1.  More  examples  of  Quetelet's  law  are  wanted: 
their  number  can  never  become  too  great. 

2.  The  curves  in  question  should  be  plotted  from  the 
same  individuals  or  from  the  same  batch  of  individuals 
in  successive  years.  The  constancy  of  their  means  and 
their  amplitude  (Galton's  0  and  Q')  should  be  deter- 
mined. Changes  in  these  values,  and  changes  in  the 
symmetry  of  the  curves,  should  if  possible  be  traced  to 
their  causes. 

3.  Polymorphic  curves  should  be  looked  for  and  ana- 
lysed. These  may  point  to  the  existence  of  mixtures  of 
perfectly  distinct  elementary  species  growing  together 
or  to  the  existence  of  antagonistic  characters  within  the 
limits  of  a  single  species  (for  examples  annual  and  bi- 
ennial forms  in  Daucits,  Beta,  etc.)  They  may  also  be 
due  to  diseases.  Finally  they  may  be  the  so-called  ''double 
curves"  in  which  the  several  apices  are  to  be  regarded 
as  ordinates  in  a  curve  of  a  higher  order,  and  not  as 
indications  of  mutation. 

4.  Correlative  variation  is  a  phenomenon  of  the  high- 
est importance.^  For  example  man  presents  many  ni- 
stances  of  correlation  between  mental  and  physical  char- 
acters. Correlations  fall  in  two  categories.  In  the  one 
are  those  cases  in  which  the  two  characters  are  dependent 
in  the  same  way  although  not  to  the  same  degree  on  ex- 

*J.  H.  BuRKiLL,  Variation  in  the  Number  of  Stamens  and  Car- 
pels, Journ.  Linn.  Soc.  Bot,  Vol.  31. 


Some  Subjects  for  Future  Investigation.         161 

ternal  conditions.  In  the  other  are  those  cases  in  which 
variation  in  one  character  is  the  cause  of  variation  in 
another/  as  for  example  the  various  phenomena  of 
growth  which  are  correlated  with  differences  in  photo- 
synthetic  activity.  It  is  superfluous  to  refer  the  reader 
to  Galton's  method  of  studying  correlation.^ 

5.  The  relation  between  external  conditions  of  life 
and  variability  ought  to  be  investigated.  Are  there  vari- 
ations which  are  independent  of  such,  or  are  there  not? 
If  there  are,  what  are  their  causes?  Do  the  individual 
external  factors  exert  a  separate  influence  or  not?  Is 
there  a  definite  relation  between  the  extent  of  this  in- 
fluence and  the  magnitude  of  the  variation?  Do  all 
characters  under  the  influence  of  high  nutrition  vary  in  a 
plus  direction,  and  under  a  poor  one  in  a  minus  direc- 
tion ?^ 

6.  The  sensitive  period  in  the  development  of  char- 
acters should  be  determined.  When  the  rudiments  of 
organs  are  visible  under  the  microscope  it  is  usually  too 
late  to  exert  any  restraining  influence  on  their  develop- 
ment. But  there  may  be  exceptions  to  this  rule.  During 
the  time  which  a  character  takes  to  develop  there  is  prob- 
ably one  short  period  of  extreme  susceptibility;  and  this 
may  be  gradually  attained  and  gradually  lost.  Here  is 
matter  for  much  interesting  inquiry. 

7.  Galton^s  regression  is  very  important.  Suppose 
we  sow  seeds  of  a  self-fertilizing  plant:  and  suppose 
that  we  know  the  amount  by  which  it  deviates  from  the 

^DuNCKER,  Roux's  Avchiv,  Vol.  VIII,  p.  163. 

^  Galton,  Natural  Inheritance,  and  Proceedings  Royal  Society, 
Vols.  40  and  45 ;  and  Ed.  Verschaffelt,  Correlaticve  Variatie  by 
planten.     Botan.  Jaarboek,  VIII,  p.  92. 

^Variability  can  also  he  influenced  by  grrafting  and  inoculation. 
See  L.  Daniel,  Compt.  Rend.,  1894,  T.  CXVIII,  p.  992. 


162  Controversial  Questions. 

mean  of  its  ancestors  in  respect  of  certain  characters. 
Then  we  determine  the  curve  describing  the  result  of 
our  sowing.  As  a  general  rule,  the  mean  of  any  char- 
acter in  the  filial  generation  departs  less  from  the  normal, 
than  the  character  in  question  borne  by  the  parent  plant 
does.  According  to  Galton,  the  relation  between  these 
two  deviations  is  a  constant  one :  the  mean  deviation 
of  the  children  amounts  to  about  a  third  of  that  of  their 
parents.  The  question  whether  this  is  a  universal  prin- 
ciple naturally  suggests  itself;  the  experiments  which 
I  have  made  hitherto  seem  to  point  to  the  conclusion 
that  it  probably  is. 

8.  Does  this  regression  remain  the  same  even  when 
selection  is  continued  for  several  generations?  In  other 
words,  does  the  mean  of  a  race  never  amount  to  more 
than  a  third  of  the  value  attained  by  the  seed  bearers 
chosen  in  every  generation?  Does  the  race  in  spite  of 
its  improvement  persist  in  this  relation  to  its  progen- 
itors, that  is  to  say,  does  it  lag  at  every  generation  rela- 
tively further  behind  the  selected  individuals  w^hich  pro- 
duced it  ?  It  seems  to  do ;  at  any  rate  the  decision  of  this 
point  dominates  the  theory  of  the  origin  of  species  by 
the  natural  selection  of  individual  variations. 

9.  OuETELET^s  law  cuablcs  us  to  calculate  from  a 
curve  of  variation  the  number  of  individuals  that  will 
exhibit  a  desired  degree  of  deviation  from  the  mean.  It 
seems  that  this  chance  even  in  the  case  of  small  differ- 
ences is  a  very  remote  one  demanding  as  it  does  millions 
of  individuals.  At  any  rate  it  is  desirable  to  make  such 
calculations   for  as  many  cases  as  possible.-^ 

10.  Artificial  selection  is  a  device  for  reaching  a  cer- 

^  See  DuNCKER,  Biolog.  Centralbl,  1898,  p.  571.  For  each  addi- 
tional 1000  individuals  the  range  of  variation  only  increases  as  from 
I  to  1.049. 


Some  Subjects  for  Future  liwestigatioii.         163 

tain  magnitude  of  deviation  from  the  average,  with  a 
minimum  expenditure  of  trouble.  Is  this  its  only  sig- 
nificance? Does  the  number  of  individuals  with  the 
undesired  qualities  diminish  exactly  at  such  a  rate  as 
we  can  calculate  beforehand?  That  is  to  sav,  is  reo^res- 
sion  independent  of  the  ancestry  of  a  given  parent;  in 
other  words,  does  it  make  any  difference  whether  the 
seed  parent  is  the  result  of  repeated  selection,  or  is 
picked  from  a  single  sowing  on  a  much  larger  scale? 

11.  In  such  experiments  attention  should  be  paid  to 
one  character  and  one  only ;  although  interesting  results 
may  often  be  obtained  by  measuring  a  second  or  even 
a  third  character  as  a  sort  of  collateral  inquiry.  The 
selections  carried  out  bv  breeders  involve  as  manv  char- 
acters  as  possible ;  on  account  of  correlations  the  improve- 
ment of  the  chief  features  can  be  carried  further  in  this 
way,  than  would  otherwise  be  possible.  Such  experi- 
ments should  be  made  with  a  purely  scientific  end  in 
view. 

12.  In  starting  an  experiment  attention  must  always 
be  paid  to  the  individual  vigor  of  the  seed-parents.  If 
this  does  not  happen  to  coincide  with  the  desired  devia- 
tion, it  is  advisable  to  take  both  the  strongest  individuals 
and  those  exhibiting  the  greatest  deviation,  as  seed- 
bearers  and  to  compare  the  posterity  of  the  two. 

13.  There  is  a  particular  kind  of  selection  experiment 
which  should  be  carried  out  a  great  deal  more  than  it  is. 
I  mean  one  which  would  start  by  choosing  as  seed- 
parents  plants  with  the  smallest  petals,  the  smallest  fruits, 
those  with  the  least  degree  of  hoariness  or  the  least  num- 
ber of  spines,  with  the  palest  color  in  their  petals,  with 
the  smallest  number  of  stamens  and  carpels  and  so  forth. 
According  to  the  theory  of  natural  selection  such  an  ex- 


164  Controversial  Questions. 

periment  should  result  in  the  origin  of  apetalous,  fruit- 
less, glabrous,  spineless,  white-flowered,  unisexual  or 
sterile  plants  and  so  forth.  Whereas  of  course  on  the 
mutation  theory  this  would  not  happen;  provided  that 
crossing  was  rigidly  excluded  from  the  experiment. 

14.  What  we  must  aim  at  is  a  complete  control  of 
variation.  We  must  become  so  thoroughly  acquainted 
with  the  underlying  factors  that  we  can  predict  the  re- 
sults of  our  experiments. 


V.   THE  ORIGIN  OF  SPECIES  BY  MUTATION. 

§   21.     SPECIES,    SUBSPECIES   AND   VARIETIES. 

We  saw  in  the  second  chapter  that  species  cannot 
have  originated  by  the  natural  selection  of  the  extreme 
variants  afforded  by  fluctuating  variability. 

We  have  therefore  now  to  show  that  the  observations 
which  have  been  made  on  this  subject  can  be  simply  and 
completely  explained  on  the  hypothesis  of  sudden  changes. 
When  such  transformations  occur  among  cultivated  plants 
— and  they  often  do — they  are  called  spontaneous  or, 
as  Darwin  called  them,  single  variations :  moreover  they 
are  almost  always  inherited,  if  not  in  their  entirety,  at 
any  rate  to  a  very  considerable  extent. 

We  may  express  therefore  the  essence  of  the  Muta- 
tion theory  in  the  words :  "Species  have  arisen  after  the 
manner  of  so-called  spontaneous  variations.''  And  in 
our  critical  survey  of  the  facts  we  therefore  have  to  con- 
sider how  far  the  information  at  our  disposal  justifies 
this  view. 

In  order  to  be  qualified  to  discuss  this  question  we 
must  first  of  all  make  quite  sure  what  we  understand  by 
the  term  "species"  and,  more  important  still,  we  must 
form  a  clear  idea  as  to  which  forms  we  are  going  to  re- 
gard as  the  units  of  the  natural  system.  For  it  is  only 
in  the  case  of  the  real  units  of  the  system  that  we  can 


166  The  Origin  of  Species  by  Mutation. 

hope  to  obtain  experimental  proof  of  their  common  de- 
scent :  the  theory  of  Descent  as  apphed  to  groups  of  these 
units  is,  and  will  probably  always  remain,  a  comparative, 
science. 

At  the  time  when  the  Linnean  view  that  species  had 
been  separately  created  was  generally  accepted,  it  was 
naturally  a  very  important  matter  to  decide  which  forms 
should  be  regarded  as  species.  I  have  already  endeavored 
to  give  some  account  of  the  broad  features  of  the  con- 
troversy which  raged  round  this  question  during  the 
period  just  before  Darwin's  work  appeared.^ 

Since  the  hypothesis  of  special  creation  of  species 
was  given  up,  the  view  that  the  Linnean  species  really  were 
the  units  of  the  system  was  fostered  by  the  persistence 
of  binary  nomenclature.  But  w^e  are  liable  to  forget 
that  these  species  do  not  correspond  to  the  units  which 
exist  in  nature,  but  to  groups  of  them.  This  is  a  fact 
which  is  clearly  recognized  and  repeatedly  asserted  by 
the  best  systematists.^  Linnaeus  himself,  as  we  have 
seen,  regarded  his  species  as  groups^  and  not  as  simple 
things,  and  De  Candolle  often  speaks  of  them  as  col- 
lective. 

The  classification  of  plants  into  groups  called  species 
has  exactly  the  same  value  and  meaning  as  their  classi- 
fication under  the  headings  of  genera,  families  and  so 
forth.  So  long  as  our  knowledge  as  to  what  are  the 
real  units  of  the  system  is  as  incomplete  as  it  is  at  pres- 
ent, systematists  and  students  of  distribution,  no  less 
than  evolutionists  will  have  to  be  content  to  deal  with 

^  See  chapter  II,  pp.  16-28. 

^Alph.  De  Candolle,  La  Phytographie',  and  De  VOrigine  des 
Especes  cultivees,  1883,  p.  372. 

^  A  good  example  of  this  is  afforded  by  the  species  Homo  sapiens. 


species,  Subspecies  and  Varieties.  167 

the  compound  Linnean  species  and  to  regard  the  small 
local  or  elementary  species  as  subsidiary  to  them.^ 

But  it  is  clear  that  this  conception  of  species  must 
result  in  incomplete  investigation  and  in  fallacious  con- 
clusions. For  example  it  is  well  known  that  the  geo- 
graphical distribution  of  species  is  analogous  to  that  of 
genera;  but  it  is  evident  that  we  should  go  far  astray 
if  we  forgot  that  species  like  genera  were  collective  enti- 
ties. The  distribution  of  elementary  species,  in  the  geo- 
graphical region  of  the  Linnean  species  which  they  com- 
pose, is  very  rarely  made  the  subject  of  inquiry,  yet  it 
is  just  this  point  which  is  of  the  very  greatest  signifi- 
cance as  bearing  both  on  the  origin  and  distribution  of 
organisms.  According  to  Jordan  every  species,  as  well 
as  every  genus,  has  a  geographical  center  where  the 
distinct  component  elementary  species  are  most  abund- 
antly represented,  growing  as  they  do  close  together  on 
the  same  spot,  whereas  at  the  circumference  of  the 
region  inhabited  by  the  species  its  elements  become  few 
and  far  between.^ 

It  is  the  actual  theory  of  descent  itself  that  would 
profit  most  by  a  proper  appreciation  of  the  conception 
of  species.  This  theory  which  is  recognized  in  mor- 
phology, embryology,  in  systematic  work  and  in  com- 
parative anatomy  as  the  guiding  principle  of  all  specu- 
lation and  inquiry  has  remained  almost  without  influence 
on  experimental  biology.  At  first  it  raised  the  hope 
that  science  would  succeed  not  only  in  discovering  the 

^  As  is  very  properly  done  in  the  classification  of  parasitic  fnnffi 
where  some  species  are  given  a  higher  rank  and  embrace  a  certain 
number  of  species  of  a  lower  rank.  See  for  example  Klebahn  in 
Pringsheim's  Jahrb.  fiir  wiss.  Botanik,  Vol.  34,  p.  395. 

^  A.  Jordan,  De  rexistence  d'especes  vegctalcs  aifincs,  1873,  pp. 
4-8. 


168  The  Origin  of  Species  by  Mutation. 

common  origin  of  all  species  but  in  bringing  the  origin 
of  species  within  the  range  of  direct  observation  and 
even  in  placing  in  our  hands  a  certain  amount  of  control 
over  these  natural  processes. 

But  we  are  to-day  just  as  far  from  this  goal  as  we 
were  in  Darwin's  time.  The  opponents  of  the  theory  of 
Descent  have  from  the  very  beginning  argued  that  we 
ought  at  least  to  be  able  to  observe  the  origin  of  species 
and,  perhaps,  even  to  effect  it  experimentally.  This  crit- 
icism must  even  now  be  recognized  as  fully  justified, 
although  it  is  of  course  no  longer  one  on  the  answer  to 
which  the  validity  of  the  doctrine  of  Descent  depends. 

It  is  just  at  this  point  that  the  prevalent  confusion 
over  species  becomes  most  evident.  What  shall  we  make 
the  object  of  observation  and  experiment?  Our  oppo- 
nents answer :  ''The  origin  of  the  ordinary  Linnean  spe- 
cies of  the  systematist."  But  these  are  artificial  groups 
whose  limits  can  be  altered  by  the  personal  taste  of  any 
systematist  and  are  indeed  as  a  matter  of  fact  much  too 
often  so  altered.  The  origin  of  such  a  species,  like  that 
of  a  genus,  is  a  historical  occurrence  and  it  can  neither 
be  repeated  experimentally,  nor  can  the  whole  process 
be  observed. 

A  plant-form  can  only  attain  the  rank  of  a  systematic 
species  by  producing  a  series  of  new  forms  and  by  the 
subsequent  elimination  of  those  which  formerly  related 
it  to  its  parent  form.  It  is  obviously  as  impossible  to 
observe  the  origin  of  an  artificially  circumscribed  group 
like  this  as  it  would  be  to  observe  that  of  a  genus  or 
familv- 

The  object  of  an  experimental  treatment  of  these 
phenomena  must  assuredly  be  to  make  the  origin  of  the 
units  which  really  exist  in  nature  the  subject  of  experi- 


species,  Subspecies  and  Varieties.  169 

ment  and  observation.  We  must  deal  not  with  the  origin 
of  the  groups  made  by  the  systematist  but  with  those 
which  are  presented  by  nature. 

There  is  no  question  that  these  elementary  species 
often  do  arise  in  the  garden  and  in  agricultural  practice. 
But  in  the  first  place  they  are  only  noticed  when  they 
have  become  established  and  when  therefore  the  chance 
of  observing  the  mode  of  their  origin  is  irrevocably  lost. 
And  in  the  second  place  we  smooth  the  matter  over  by 
calling  the  new  forms  "Varieties." 

What  are  varieties?  In  wild  plants  they  are  usually 
very  different  from  what  they  are  in  cultivated  ones. 
Or  rather  the  term  variety  has  a  number  of  definitions 
none  of  which  is  definite  enough.  In  the  eyes  of  those 
who  perhaps  unconsciously  were  anxious  to  maintain  the 
supernatural  value  of  species — and  there  are  many  of 
them  even  now — all  forms,  not  the  result  of  crossing, 
the  history  of  whose  origin  is  more  or  less  accurately 
known,  are  called  "varieties,"  Thus,  all  elementary  spe- 
cies arising  under  cultivation  fall  into  this  category. 
Gardeners  as  a  rule  often  draw  no  distinction  between 
"varieties"  and  "kinds"  on  the  one  hand  and  between 
these  and  species  and  hybrids  on  the  other. 

The  description  of  all  forms  with  whose  origin  we 
are  familiar,  as  varieties,  opens  the  door  to  endless  misuse 
of  the  term.  On  this  ground  alone  therefore  it  ought  to 
be  given  up.  Even  some  of  the  best  known  authors  of 
pre-Darwinian  days  thought  that  they  could  prove  the 
common  origin  of  a  group  of  species  by  describing  them 
as  varieties  of  a  species  of  a  higher  order.  In  this  way 
Naudin  for  example,  according  to  Wallace,  "proved" 
that  the  thirty  species  of  melons,  which  had  been  recog- 


170  The  Origin  of  Species  by  Mutation. 

nized  up  to  that  time,  were  only  varieties  ^  And  it  will 
obviously  continue  to  be  impossible  to  demonstrate  the 
origin  of  a  "species"  so  long  as  this  demonstration  is 
regarded  as  ''degrading"  the  form  in  question  to  the 
rank  of  a  variety.  This  would  become  a  mere  juggling 
with  words. 

The  conception  of  a  variety  held  by  those  who  are 
the  best  qualified  to  judge,  rests  on  the  view  that  a  single 
character  is  not  sufficient  to  confer  specific  rank  on  a 
given  form.  A  beautiful  example  is  afforded  by  the  case 
which  we  have  already  mentioned  of  Datura  Stramonium 
and  Datura  Tatula.  Each  was  regarded  as  a  species  by 
Linnaeus  himself,  but  they  have  been  united  to  form 
a  single  species  by  more  recent  authors  on  the  ground 
that  Tatula  is  only  distinguished  from  Stramoniwn  by 
the  possession  of  a  blue  pigment  in  its  flowers,  stem  and 
petioles.^ 

This  limitation  of  the  idea  of  a  variety  is  manifestly 
desirable  scientifically,  especially  for  the  reason  that  the 
distinguishing  feature  is  very  often  due  to  the  loss  or 
latency  of  a  character:  absence  of  Petals,  of  Hairs,  of 
Thorns,  of  Color  in  the  flower  and  so  forth.  Such  cases 
afford  the  best  examples  of  what  we  ought  to  call  a  vari- 
ety. But  it  should  not  be  forgotten  that  the  evidence  for 
the  relationship  of  such  forms  to  their  species  ordinarily 
rests  only  on  analogy ;  and  not,  or  very  rarely,  on  actual 
proof. 

Such  varieties  are  just  as  distinct  and  just  as  constant 
in  cultivation  as  the  best  species.  If  it  is  still  considered 
proper  that  they  should  be  called  varieties,  then  it  fol- 

^  Wallace^  Darwinism,  p.  87 

^  In  my  opinion,  Siramoninm  is  regarded  quite  wrongly  as  the 
species  and  Tatula  as  the  variety.  Every  analogy  points  to  the  blue 
as  the  older  and  the  white  as  the  younger  form  (See  Fig.  5  on  p.  31). 


species,  Subspecies  and  Varieties.  171 

lows  that  varieties  are  nothing  less  than  a  particular 
form  of  species.  Varieties  are  only  small  species,  as 
Darwin  has  said.^ 

Jordan's  elementary  species  are  distinguished  from 
one  another  not  by  one  peculiarity  but  in  nearly  all  their 
characters.  This  is  an  extremely  important  point.  There 
is  absolutely  no  justification  for  regarding  them  as  vari- 
eties. If  we  wish  to  treat  them  as  subdivisions  of  the 
old  species  they  must  be  called  subspecies.  I  prefer  to 
call  them  elementary  species.  Darwin  speaks  repeatedly 
of  specific  elements  when  he  is  referring  to  their  indi- 
vidual characters.^ 

There  is  little  prospect  that  an  agreement  between 
all  the  workers  in  this  field  will  ever  be  brought  about. 
Theoretically  in  my  opinion  we  should  be  perfectly  justi- 
fied in  applying  the  coveted  distinction  of  ''species"  to 
these  elementary  forms,  whose  limits  are  not  set  by  our 
imagination.  But  practically  it  is  for  many  reasons  more 
convenient  to  refer  to  the  artificial  groups  of  these,  that 
is,  the  collective  species,  simply  as  species.  Where  we 
are  concerned  with  the  investigation  of  the  origin  of  a 
single  species  we  mean  of  course  an  elementary  one. 
The  other  species  are  groups  whose  origin  is  a  matter 
of  history  and  cannot  for  this  reason  be  dealt  with  ex- 
perimentally. 

Thus  we  see  that  Linnean  species  are  collective  and 

artificial   whilst   Jordan^'s   species   are   single   and    real. 

Each  collective  species  consists  of  a  larger  or  smaller 

group  of  subspecies  or  elementary  species;  in  the  deter- 

'^  Life  and  Letters,  II.  p.  T05.  Darwin's  more  famous  aphorism 
that  varieties  are  incipient  species  is  less  happy.  We  know  nothing 
about  the  age  of  most  varieties. 

^  E.  g.,  Variations  in  Animals  and  Plants,  IT.  p.  23.  Each  of 
these  elements  is  represented  in  the  germ,  according  to  the  theory 
of  Pangenesis,  by  a  unit,  the  Pangene. 


172  The  Origin  of  Species  by  Mutation. 

mi  nation  of  the  limits  of  these  groups  the  systematist 
is  guided  almost  entirely  by  the  gaps  which  have  arisen 
by  the  disappearance  of  more  or  less  numerous  sub- 
species. 

With  regard  to  the  nomenclature,  it  would  perhaps 
be  better  if  the  binary  system  were  replaced  by  a  ternary; 
to  retain  the  Linnean  specific  names  as  much  as  possible 
and  to  write  after  them  the  name  of  the  elementary 
form.i  The  idea  of  a  variety  should  be  strictly  confined 
to  cultivated  forms. ^ 

§  22.    SPECIES  IN  NATURE. 

The  species  of  the  systematist  are  compound  species; 
they  consist  of  a  greater  or  smaller  number  of  subspecies 
which  breed  true  when  tested.  The  larger  the  geograph- 
ical area  inhabited  by  a  species,  the  larger  is  the  number 
of  component  subspecies :  they  are  concentrated  in  the 
center  of  the  area  and  become  scattered  towards  its  per- 
iphery. 

In  local  floras  therefore  as  a  rule  each  species  con- 
sists of  only  one  or  very  few  elementary  species.^  The 
species  of  such  local  floras  do  not  exactly  agree  in  neigh- 
boring districts.^     From  France  alone  Jordan  brought 

^  This  course  is  adopted  by  Waagen  in  Benecke,  Geognostisch- 
paldontologische  Beitragc ,  1876,  Vol.  2,  p.  187. — An  example:  any  one 
can  guess  the  meaning  of  Draba  verna  leptophylla  whilst  Erophila 
leptophylla  has  no  meaning  except  to  the  initiated. 

^  Subspecies  are  not  to  be  regarded  as  subsidiary  to,  nor  as  de- 
rived from  the  species ;  for  each  species  consists  of  a  group  of  sub- 
species. The  only  thing  that  can  be  said  in  favor  of  the  conventional 
assumption  of  a  forma  genuina  is  that  it  is  convenient. 

^  Only  one  elementary  species  of  Draba  verna  so  far  as  I  can 
find  occurs  round  Amsterdam  and  the  towns  in  its  neighborhood: 
it  agrees  with  Jordan's  D.  leptophylla. 

■*  For  example  Senecio  Jacohaea  is  common  in  the  neighborhood 
of  Haarlem,  but  always  without  ray-florets,  whereas  in  the  adjoin- 
ing dunes  near  Leiden  it  is  only  found  with  these  florets. 


species  in  Nature.  173 

together  over  50  species  of  Draba  verna^  in  his  garden,^ 
and  from  other  countries  in  Europe,  especially  from  Eng- 
land, Italy  and  Austria,  about  150  more,  so  that  in  1873 
he  had  more  than  200  forms  in  cultivation.^ 

This  richness  in  forms,  or  polymorphism  as  it  is 
called,  of  the  so-called  *'good"  species  is  quite  a  general 
phenomenon.^  Darwin  repeatedly  called  attention  to 
it  and  argued  that  as  a  result  of  it  the  most  widely  dis- 
tributed types  had  the  best  chance  of  giving  rise  to  new 
species  and  so  of  gradually  becoming  genera. •"*  In  the 
case  of  rare  forms  he  showed  the  prospect  of  doing  so 
to  be  much  smaller. 

Very  few  plants  are  as  rich  in  subspecies  as  Draba 
verna.  Perhaps  Viola  tricolor  comes  next^  with  its 
well-known  subspecies  Viola  arvensis  which  is  itself 
a  collective  form.'^  In  Germany  or  France  the  average 
number  of  subspecies  per  species  may  be  placed  at  2  or  3, 
for  the  whole  of  Europe  the  average  is  perhaps  about  10. 
If  all  these  forms  were  noted  and  described  the  Flora  of 
Europe  would  be  increased  tenfold,  which  would  be  most 
inconvenient.  But  just  as  there  are  valuable  treatises 
which  only  deal  with  the  genera  or  at  any  rate  only  with 
these  and  their  more  important  species,  so  it  would  be 
the  business  of  the  ordinary  Floras  to  describe  the  species 
and  their  more  important  subspecies.     The  task  of  deal- 

^  See  Fig.  3  on  page  22. 

^  Dc  I'origine  dcs  arhrcs  fniitiers,  1853. 

^  Dcs  cspcces  vcgetales,  aiRnes,  p.  13,  1873. 

*It  is  often  spoken  of  as  "Variability":  but  this  cannot  conceal 
the  fact  that  the  elementary  species  which  compose  the  species  are 
constant,  and  independent  of  one  another. 

^  Wallace^  Darzuinism,  p.  80  and  98. 

®  A.  Jordan,  Observations  snr  plusieurs  plantcs  nouvelles,  1846- 
1849,  Vol.  II,  p.  7. 

"^  See  Fig.  4  on  page  23. 


174 


The  Origin  of  Species  by  Mutation. 


ing  with  all  the  elementary  forms  that  exist  must  be  the 
duty  of  monographs  of  a  greater  degree  of  completeness.^ 
When  it  is  a  question  of  the  origin  of  one  elementary 
species  from  another  this  material  is  absolutely  essential 
to  the  student  of  evolution.  When  however  our  object 
is  the  study  of  the  relationship  of  the  larger  groups  it 
certainly  constitutes  a  mere  dead  weight,  the  fact  of 
whose  existence  one  is  only  too  often  tempted  to  sup- 
press. But  I  can  see  no  rea- 
son why  these  two  branches 
of  inquiry  should  not  exist 
side  by  side.  Nothing  but 
a  belief  in  the  supernatural 
value  of  the  Linnean  species 
can  stand  in  the  way. 

In  the  natural  state  it  iS 
only  very  rarely  that  ele- 
mentary species  are  distin- 
guished by  a  single  or  by 
two  or  three  characters- 
(Fig.  ?)2>)  ;  they  usually  dif- 
fer in  all  their  organs  and 
characters.  A  complete  diagnosis  often  requires  a  whole 
page.  The  tout  ensemble  of  the  plant  is  quite  distinctive ; 
and  the  practised  eye  can  recognize  the  various  forms 
at  a  distance.^     This  is  especially  so  in  the  case  of  cul- 

^  Compare,  for  example,  the  Flora  Europae  of  M.  Gandoger, 
which  gives  the  elementary  forms  for  all  the  more  important  species, 
but  only  refers  to  their  characters  in  short  dichotomous  tables  {27 
vol.). 

'On  the  heaths  near  Amsterdam  there  are  to  be  found  three 
forms  of  Potcntilla  Tormentilla,  one  with  narrow,  one  with  broad 
and  one  with  intermediate  petals ;  I  saved  seeds  from  each  of  these 
forms  and  found  them  to  be  constant. 

^  Or  they  may  be  quite  or  nearly  indistinguishable  externally  and 
differ  from  one  another  only  in  fundamental  physiological  characters 
as  for  example  in  the  choice  of  hosts  in  the  case  of  the  Rusts — facts 


Fig.  22)-  Potentilla  Tormentilla, 
with  narrow,  broad  and  inter- 
mediate petals  representing 
three  constant  subspecies 
found  in  nature. 


species  ill  Nature.  175 

tures  where  groups  of  many  individuals  of  the  different 
types  grow  close  together.  The  characters  are  sometimes 
of  such  a  kind  that  they  are  easily  recognizable  even  on 
dried  material;  but  they  very  often  disappear  entirely 
or  partly  when  the  plants  are  pressed. 

The  constancy  and  thus  the  distinctness  of  the  local 
species  can  only  be  proved  by  cultivating  the  plants  from 
seed.-^  Experiments  of  this  kind  have  been  carried  out 
on  a  large  scale  by  Koch  and  Fries  and  other  well- 
known  systematists  but  especially  by  Jordan  and  his 
pupils.  In  many  cases  these  experiments  have  been  re- 
peated and  always  with  the  same  result.  Thuret  and 
Bonnet  grew  14  of  Jordan^s  species  of  Draba  verna, 
4-6  species  of  Papaver  dnhiinn,  for  about  7  years  and 
convinced  themselves  of  the  constancy  of  these  forms.^ 

This  statement  is  supported  by  the  high  authority  of 
De  Bary,  who  satisfied  himself  as  to  the  constancy  and 
systematic  distinctness  of  the  numerous  subspecies  of 
Draba  verna,^  as  the  result  of  his  well-known  researches, 
which  were  continued  and  published  after  his  death  by 
F.  Rosen.  This  splendid  work  has  received  full  recog- 
nition, but  it  has  not  had  the  effect  which  De  Bary  evi- 
dently hoped  it  would  have  on  his  contemporaries,  of 
directing  research  more  generally  into  these  channels. 

A  similar  state  of  affairs  obtains  in  zoology.  Every 
?oologist  knows,  as  Bateson  remarks,^  that  in  the  case 
which  we  owe  to  the  exhaustive  and  important  researches  of  Ericks- 

SON. 

^  Conclusions  based  on  comparative  study  only  should  never  he 
regarded  as  proofs  in  this  field.    See  the  Flora  Europae  of  Gandoger. 

^J.  CosTANTiN,  Accomodation  dcs  plantcs,  Bull,  scientif.  publie 
par  GiARD,  Vol.  XXXI,  p.  507. 

^  F.  Rosen,  Systematische  und  biologische  Beohachtungen  iiber 
Erophila  verna,  Bot.  Zeitung,  1889,  No.  35. 

*  W.  Bateson,  On  Progress  in  the  Study  of  Variation,  Science 
Progress,  Vols.  I  and  II,  1897-98.    Vol.  II,  p.  i. 


176  The  Origin  of  Species  by  Mutation. 

of  many  species  the  individuals  differ  according  to  the 
region  which  they  inhabit,  and  that  by  means  of  these 
differences  the  species  can  be  spht  up  into  local  races. 
The  differences  may  be  very  slight  and  often  only  vis- 
ible to  the  initiated,  and  yet  perfectly  (Constant.  But 
these  facts  are  far  from  being  appreciated  as  much  as 
they  deserve.-^ 


§  23.    SPECIES  IN   CULTIVATION. 

Just  as  wild  species  at  present  consist  of  a  larger  or 
smaller  number  of  constant  and  independent  subspecies, 
so  presumably  will  it  have  been  with  those  species  which 
man  has  brought  into  cultivation. 

Pliny  was  acquainted  with  the  different  kinds  of  a 
number  of  fruit  trees,  for  example  43  sorts  of  pears, 
29  of  apples,  10  of  plums,  8  of  cherries  and  so  forth. 
The  Romans  knew  at  least  two  sorts  of  beet,  several 
kinds  of  which  grow  wild  in  the  Mediterranean  region. 

In  about  the  year  1600  Olivier  de  Serres  described 
in  his  Theatre  d' agriculture  the  cultivated  plants  that 
were  known  at  that  time.  He  refers  also  to  the  main 
types  of  our  modern  vegetables.  He  mentions  61  vari- 
eties of  pears,  and  51  of  apples,  and  also  the  commonly 
grown  sorts  of  beet.  Whence  all  these  forms  arose  we 
do  not  know.  It  is  possible  that  they  arose  in  cultiva- 
tion; it  is  even  possible  that  they  arose  as  the  result  of 
cultivation.  But  it  is  equally  possible  that  they  existed  be- 
fore it,  growing  wild  either  together  or  in  different  places, 
and  that  all  or  most  of  them  were  taken  over  into  culti- 
vation as  such.  For  there  is  absolutely  no  ground  for 
the  belief  that  the  plants  known  to  agriculture  were  only 

^  See  also  Duncker,  Roux's  Archiv,  Vol.  VIII,  1899,  P-  164. 


species  in  Cultivation.  \77 

once   found   by  man   in   nature  and  only  once  brouglit 
into  cultivation. 

So  long  as  the  chief  concern  of  biologists  was  to 
establish  the  theory  of  descent  there  was  some  use  in 
elaborating  the  probabilities  in  this  sphere.  But  now, 
it  seems  to  me  that  it  w^ill  suffice  if  we  recognize  the  lack 
of  historical  information  on  this  point. 

.A  favorite  theme  for  discussion  is  the  question 
whether  wheat  owes  its  origin  to  a  few  or  to  many  wild 
forms.  For  whether  we  are  to  assume  that  wheat  has 
"varied"  in  a  large  or  small  degree  during  its  cultivation 
depends  on  the  answer  to  this  question.  It  seems  far 
more  likely  that  wheat,  just  like  Draba  verna,  was  orig- 
inally composed  of  a  vast  assemblage  of  subspecies  in 
the  wild  state.  ^  And  as  fertilization  in  wdieat  takes  place 
mainly  before  the  flowers  are  open,  it  is  evident  that 
many  kinds  can  maintain  themselves  side  by  side  in  the 
same  field,  provided  of  course  that  they  are  really  con- 
stant. 

The  history  of  this  subject  contains  a  chapter  which 
has  a  very  strong  bearing  on  this  point.  It  concerns 
Colonel  Le  Couteur's  cultivations  in  Jersey  at  the  be- 
ginning of  the  nineteenth  century.-  He  was  visited  by 
Professor  La  Gasca  who  pointed  out  to  him  that  his 
field  of  wheat,  far  from  being  a  uniform  culture,  con- 
sisted of  at  least  23  distinct  sorts  growing  together.  The 
natural  supposition  was  that  some  of  these  sorts  would 
have  a  larger  share  in  the  harvest  than  others.  Le  Cou- 
TEUR  therefore  harvested  the  seeds  of  typical  individuals 
of  these   sorts   separately  and   carried  out  comparative 

^  Of  all  cultivated  plants  the  cereals  have  changed  least  accord- 
ing to  De  Candolle  in  I'Origine  des  cspcces  ciiltivces. 

^VoN  RiJMKER.  Gclreidesiichtung,  p.  67. 


178  The  Origin  of  Species  by  Mutation. 

sowings  of  pure  bred  kinds  for  a  space  of  a  few  years 
to  find  out  which  of  them  were  the  most  valuable.  The 
offspring  of  these  sorts  proved  to  be  pure  and  constant; 
and  his  original  field  must  therefore  have  contained 
simply  a  mixture  of  these  sorts.  Le  Couteur  continued 
to  grow  the  best  of  the  kinds  thus  purified  with  such 
success  that  he  put  them  on  the  market  with  no  small 
advantage  to  himself;  even  now  some  of  them  are  still 
very  well  known,  as  for  example  the  Bcllevne  dc  Tala- 
vera. 

Wheat  was  therefore  at  that  time  a  mixture  of  dif- 
ferent sorts;  Le  Couteur  seems  to  have  been  the  very 
first  to  isolate  these  units.  ^  And  even  now  the  common 
types  of  wheat  are  still  mixtures.  The  mixture  main- 
tains itself  without  artificial  selection,  but  the  pure  form 
does  not.^ 

Later,  Patrick  Shirreff  in  Scotland  worked  on  the 
same  lines  as  Le  Couteur  w^ith  various  forms  of  cereals. 
He  used  to  look  in  his  own  fields  and  in  those  of  his 
friends  for  striking  and  apparently  better  examples :  then 
he  sowed  their  seeds  separately  and  examined  their  off- 
spring. As  a  rule  they  turned  out  to  be  constant  and 
often  very  productive.  In  this  way  he  found  the  original 
of  Mungo  swells  wheat  in  1819,  Hopetozvn  oats  in  1824, 
Hopetozvn  wheat  in  1832,  and  later  Shirreff' s  oafs.^ 
They  were  absolutely  constant  and  as  soon  as  a  sufficient 
quantity  of  seed  had  been  obtained  by  cultivation  for  two 

^  At  that  time  nobody  thought  of  improvement :  the  idea  did  not 
arise  till  about  50  years  later. 

^  See  p.  98. 

'  V.  RiJMKER,  loc.  cit.,  p.  70.  See  also  the  account  of  Dr.  Hesse's 
travels  in  Landw.  Jahrb.,  VI,  1877,  p.  850  et  seq.,  and  Shirreff's 
Improvement  of  Cereals,  London,  1873. 


species  in  Cultivation.  179 

or  three  generations  they  were  put  on  the  market  without 
further  selection. 

Space  does  not  permit  us  to  treat  further  of  Le  Cou- 
teur's  and  Patrick  Shirreff's  work.  Suffice  it  to 
say  that  they  show  us  in  a  general  way  that  wheat,  barley 
and  oats^  were  at  that  time  mixtures  of  perfectly  con- 
stant subspecies  exactly  as  we  have  seen  that  the  species 
of  wild  plants  are.  '  But  we  know  as  little  about  their 
origin  in  the  one  case  as  we  do  in  the  other. 

One  of  the  most  frequently  discussed  questions  in 
practical  horticulture  is  that  of  the  origin  of  fruit  trees, 
especially  of  the  modern  improved  kinds  of  apples  and 
pears.  There  is  no  doubt  about  the  common  origin  of 
these  forms.  The  question  is  only  whether  their  common 
origin  merely  follows  from  the  theory  of  descent  or 
whether  it  is  historically  traceable.  The  latter  is  cer- 
tainly not  the  case  with  most  of  the  chief  types ;  the  past 
history  is  only  known  with  certainty  in  the  case  of  some 
of  the  recent  sorts. 

It  is  to  the  Belgian  breeder  Van  Mons  that  we  owe 
the  most  valuable  information  on  this  subject  that  we 
possess.  In  the  first  half  of  the  nineteenth  century  he 
put  many  of  our  well-known  kinds  on  the  market.- 

^  Rye,  which  may  be  wind- fertilized,  behaves  differently. 

^The  literature  on  this  subject  seems  to  be  little  known  and  is 
difficult  to  get  hold  of :  I  have  not  succeeded  in  seeing  the  works  of 
PoiTEAU  and  Chandeze.  The  following  is  a  list  of  the  most  im- 
portant : 

Van  Mons,  Arbrcs  fruifiers  ou  Pomonomic  beige,  2  vols,   1835. 
Quotations  from  it  will  be  found  in  Jordan's  Arbres  fruitiers, 
pp.  38  and  94.. 
PoiTEAU,    Theorie    de    Van   Mons   ou    notice   historiquc   sur    les 
moyens  qu'emploie  Van  Mons  pour  obtenir  d'cxccUents  fruits 
de  semis.     Ann.  Soc.  d'Agric,  Paris,  1834,  Vol.  15. 
G.  Chandeze,  La  Theorie  de  Van  Mons  concernant  la  production 
de  nouvelles  varietes  fruitier es.     Belgique  horticole,    1877,  p. 
354-    Bot.  Jahrb.,  V,  p.  761. 
GoDRON,  De  VEspcce,  II,  p.  loi. 


180  The  Origin  of  Species  by  Mutation. 

Van  Mons  expressly  stated  that  he  himself  had  not 
originated  any  new  forms:  "La  nature  seule  cree.''^     He 
found  all  the  sorts  which  he  cultivated  and  put  on  the 
market,  growing  as  such  in  the  wild  state^  and,   as  it 
happened,  almost  all  of  them  in  the  Ardennes.     The  wild 
plants  were  thorny   and  their   fruits   small,   tough  and 
woody.     As  the  result  of  being  sown  in  a  garden  and 
under  the  influence  of  another  climate^  they  regularly 
lose  their  thorns  and  the  tough  consistency  of  their  fruits, 
which  become  larger,  fleshier  and  juicier.     But  the  dif- 
ferences in  form,  color  and  taste  and  other  valuable  char- 
acters arose  neither  in,  nor  as  a  result  of,  cultivation ;  they 
already  existed  in  the  wild  forms.     His  new  kinds  are 
nothing  more  nor  less  than  already  well-known  cultivated 
forms'*  which  he  has  improved  in  respect  of  size  and 
juiciness,    by    selection    for   two   or   three   generations'* 
without   altering  their   varietal   characters   in   the   very 
least. ^    Van  Mons  was  fully  aware  of  the  independence 
and  constancy  of  these   forms  and  it  should  be  noted 
that  he  speaks  of  them  as  subspecies  and  not  as  varieties. 

The  best  way  to  raise  a  new  type  for  the  market  is 
not  to  sow  the  seeds  of  the  best  sorts  already  in  culti- 
vation but  those  of  a  fruit  which,  be  it  ever  so  puny, 
belongs  to  a  hitherto  unknown  type. 

It  seems  that  most  of  the  new  sorts  that  have  been 
raised  by  other  breeders  have  arisen  in  the  same  way. 
For  example  the  splendid  St.  Germain  pear  owes  its  ori- 
gin to  a  single  tree  found  by  chance  in  the  Foret  de  St. 
Germain  near  Paris;  Besy  de  Charnnontel,  Bergamotte 
Sylvanche,  and  Virgoideuse  are  also  due  to  a  lucky  find. 

^  Pomonomie,  I,  p.  445,  *Loc.  cit.,  II,  p.  208. 

^Loc.  cit.,  p.  406,  444.  ^Loc.  cit.,  p.  462  and  II,  p.  208. 

^ Loc.  cit.,  p.  410.  "" Loc.  cit.,  T,  p.  415. 


species  in  Cultivation.  181 

Bailey^  has  recently  given  a  very  striking  example 
w^hich  illustrates  this  point.  Mr.  Peter  M.  Gideon  sowed 
a  vast  number  of  apple  seeds  and  from  these  he  got  a 
single  plant  whose  fruit  he  ultimately  put  on  the  market 
as  the  Wealthy  Apple,  because  he  made  his  fortune  by 
it.  This  apple  is  now  one  of  the  most  favorite  and 
widely  known  in  Minnesota. 

Mr.  Gideon  tells  the  story  of  how  he  got  this  mag- 
nificent fruit  as  follows.  For  nine  years  he  sowed  apple 
seeds  so  as  to  raise  about  a  thousand  young  trees  every 
year.  But  all  this  led  to  no  result.  Then  he  happened 
to  buy  a  small  basket  of  apples  of  a  foreign  kind  in 
Maine :  they  provided  him  with  about  50  seeds  from  one 
of  which  his  Wealthy  Apple  arose.  Sowing  on  a  large 
scale  had  no  result ;  sowing  on  a  small  scale  but  from 
a  new  form  fulfilled  his  highest  expectations. 

Our  argument  is  supported  by  the  following  evidence. 
If  apples  and  pears  are  allowed  to  grow  wild  they  are 
well  known  to  revert  to  the  type  of  the  crab-apple  and  the 
wild  pear  in  a  few  generations.  But  each  sort  retains 
the  features  characteristic  of  it ;  they  do  not  all  revert  to 
one  and  the  same  wild  form. 

Whence  does  the  host  of  wild  sorts  of  apples  and 
pears  arise?  We  do  not  know.  There  are  some  who 
assert  that  they  have  arisen  in  cultivation  and  have  then 
run  wild.  But  this  would  hardly  account  for  the  large 
number  of  new  sorts  that  have  been  obtained. 

It  is  the  same  with  most  cultivated  plants  as  it  is  with 
cereals  and  fruit  trees :  almost  every  species  consists  of 
more  or  less  numerous  subspecies  about  whose  origin  we 
know  nothing  at  all. 

Flax,  the  red  clover  and  the  poppy  are  very  good 

^  L.  H.  Bailey,  Plant-breeding,  New  York,  1896.  p.  108. 


182 


The  Origin  of  Species  by  Mutation. 


examples  of  plants  with  such  subspecies.  The  chief  types 
of  Chrysantheuimn  indicum  were  imported  as  such  from 
Japan  into  Europe ;  the  newer  sorts  have  almost  all  been 
obtained  by  crossing  them.  A  great  variety  of  other 
examples  can  be  easily  collected. 


Fig.  34.   Scduui  crispiim  after  ]Munting,  1671. 


Many  so-called  \'arieties  and  even  many  monstrosi- 
ties have  been  known  since  the  time  when  the  species  to 

'^Abraham  Munting,  Waarc  Oeffeninge  der  Planten,  1671,  p. 
237.  Hunting's  Sedum  crispuiii  evidently  is  the  same  as  Sediim 
cristatum  Schrad.  {Sedum  reiiexum  cristatum)  ;  the  monstrosity 
must  therefore  be  more  than  two  centuries  old.  Since  Hunting's 
time  fasciation  in  this  species  has  repeatedly  been  observed  and 
recorded.  Cf.  Penzig,  Teratologie,  I,  p.  467.  The  character  is 
strongly  inherited.  I  raised  from  seed  a  square-meter  bed  full  of 
plants  with  more  or  less  flattened  branches,  some  of  which  I  have 
photographed  and  reproduced  in  Fig.  35.  Normal  cylindrical  or 
atavistic  branches  are  shown  both  in  the  above  figure  from  Hunting 
and  in  that  from  my  own  culture  (Fig.  35  at). 


species  in  Cultivation. 


183 


which  they  belong  were  introduced;  and  have  been  de- 
scribed and  drawn  in  early  works  on  the  subject.  Abra- 
ham Hunting  gave  a  long  list  of  them  in  the  year  1671.^ 
In  it  will  be  found  examples  of  double  flowers  of  Vinca, 
Colchicum,  Hepatica,  Cardaniine,  Cheiranthiis  Cheiri, 
Papaver,  Viola,  Caltha,  Althaea,  and  others;  of  white- 
flowered  forms  of  Ononis,  Syringa,  Centaiirea,  Digitalis, 
Fritillaria,   Hepatica   besides   white   strawberries,   white 


Fig.  35.    Scdum  rcUexum  crisfatum.     From  nature,  1900,  with 
expanded  and  ordinary  (at)  branches. 

raspberries  and  red  gooseberries,  and  double  Bellis  and 
Matricaria.  Also  proliferating  forms  of  Bellis,  Calen- 
dula, Heliantlms  and  Scabiosa,  fasciated  Crown  Impe- 
rials, Plantago  major  rosea.  Primula  veris,  and  P.  Auri- 
cula with  a  double  Corolla,  fasciated  Seduni  ( Figs.  34 
and  35),  Celosia  cristata,  Amaranthus  cristatus,  etc. 

Moreover  hundreds  of  varieties  of  the  more  impor- 
tant garden  plants,  e.  g..  Hyacinths,  Tulips  and  Ranun- 
culus were  known  at  that  time. 

^  Waarc  Ocffeninge  der  Planten,  Groningcn.  1671. 


184  The  Origin  of  Species  by  Mutation. 

Many  forms  which  are  put  on  the  market  as  new  are, 
from  our  point  of  view,  really  quite  old.  I  mention  as  an 
example  the  famous  double  Lilacs  which  Victor  Lemoine 
of  Nancy  put  on  the  market  in  the  '80's.  They  consist  of 
a  number  of  new^  and  in  many  respects  excellent  varieties 
which  have  now  found  a  place  in  many  gardens  and  parks. 
Thev  were  offered  as  new ;  and  I  was  anxious  to  find  out 
how  the  ^'doubling"  had  been  attained.  I  went,  therefore, 
in  1892  to  Nancy  and  asked  M.  Lemoine.  After  he  had 
shown  me  his  plantations  of  Lilac  he  told  me  the  follow- 
ing story  of  their  origin.  "In  1870  I  happened  to  see  in 
a  garden  in  Luxembourg,  a  double  specimen  of  Syringa 
vulgaris  azure  a  plena,  a  little-known  form  which  is  seldom 
seen  in  gardens.  When  some  years  later  I  came  to  think 
of  growing  Lilacs  I  simply  bought  this  plant  and  crossed 
it  with  almost  every  variety  on  the  market."  This  was 
the  way  in  which  he  got  his  novelties.  But  as  to  the 
origin  of  doubling  he  was  completely  in  the  dark.  Later 
I  found  that  Hunting  had  mentioned  the  double  form 
as  early  as  1671. 

We  know  just  as  little  about  the  origin  of  the  Cactus- 
dahlias  which  threaten  to  supersede  all  other  kinds  owing 
to  their  great  variety,  and  to  the  splendor  of  their  flow- 
ers. They  are  the  result  of  a  cross  between  one  single 
plant  and  numerous  older  varieties.  When  I  visited  Mr. 
Van  den  Berg  in  Jutphaas  who  introduced  this  novelty, 
he  gave  the  following  account :  "Many  years  back  (1872) 
I  asked  a  correspondent  of  mine  in  Mexico  to  send  me 
a  case  of  bulbs,  roots  or  rhizomes  of  any  kind  of  foreign 
plants  he  could  possibly  get  hold  of.  The  contents  of 
the  box  reached  Holland  in  very  bad  condition :  almost 
everything  was  rotten;  in  fact  everything  but  a  single 
tuber  which  however  produced  a  shoot.     This  plant  was 


species  mid  Specific  Characters.  185 

the  first  C actus-T)3h\\2i.  All  efforts  to  find  the  same  form, 
in  the  district  where  my  correspondent  lived,  were  in 
vain."^  The  plant  was  there;  but  how  it  arose  we  do 
not  know. 

It  is  just  the  same  in  many  other  cases,  and  with  the 
most  important  types  too.  The  breeder  is  delighted  when 
he  sees  a  new  form ;  but  as  to  how  it  arises  he  is  generally 
ignorant.  It  often  happens  that  they  arise  singly  in 
sowings  on  an  enormous  scale ;  in  which  there  is  a  greater 
likelihood  that  the  seeds  will  be  of  different  stocks,  than 
in  small  ones.  In  this  way  D.  B.  Wier  got  his  cutleaved 
maple  in  a  sowing  of  about  a  milHon  seedlings.^  And  in 
the  same  way  Donkelaar  got  the  first  double  Dahlias 
in  a  culture  of  about  10,000  plants,  and  so  forth. 

There  is  no  object  in  citing  more  instances  especially 
as  most  of  the  early  ones  are  to  be  found  in  Darwin^s 
works. 

We  may  conclude  therefore  that  even  among  culti- 
vated plants,  species  are  mixtures ;  consisting,  as  they  do, 
of  independent  often  numerous  sorts  of  subspecies  which 
have  been  found  as  such  in  the  wild  state.  This  fact  is 
well  known  to  many  breeders  and  botanists :  though  the 
earlier  botanists  were  more  familiar  with  it  than  modern 
ones  are.  Hence  the  often  repeated  saying,^  'Tf  you 
want  to  raise  a  novelty  you  must  first  possess  it!" 

§  24.    SPECIES  AND  SPECIFIC  CHARACTERS. 

The  reader  is  now  in  a  position  to  understand  what 
I  mean  when  I  say  that  our  business  is  not  really  with 

^  See  Van  den  Berg,  in  Gardeners'  Chronicle,  Nov.  8,  1879;  and 
W.  Miller,  The  Dahlia,  in  Bull.  Ithaca,  No.  128,  p.  127. 

^L.  H.  Bailey,  Plant-breeding,  1896,  p.  109. 

^  Jordan,  Arhres,  fruitiers,  p.  96. 


186  The  Origin  of  Species  by  Mutation. 

the  origin  of  species  but  with  the  development  of  specific 
characters. 

The  diversity  of  organic  forms  is  due  to  the  existence 
of  a  vast  number  of  differentiating  characters.  And  the 
question  we  have  to  answer  is  ''how  have  these  characters 
arisen?" 

Subspecies  become  species  by  extinction  of  inter- 
mediate forms.  New  species  can  arise  by  crossing  when 
the  pecuHarities  of  two  forms  already  existing  are  united 
to  form  a  single  new  one ;  and  so  on.  But  these  are  not 
cases  of  the  origin  of  specific  characters.  Many  species 
and  even  genera  and  still  larger  systematic  groups  have 
arisen  by  these  characters  disappearing  or  becoming  la- 
tent. The  origin  of  the  monocotyledons  from  the  dicoty- 
ledons is  regarded  by  some  as  coming  under  this  head 
(Delpino).  But  loss  and  latency  are  obviously  special 
cases  which  do  not  directly  touch  the  main  question  of 
progress  in  the  animal  and  vegetable  kingdom. 

The  question  is  not  how  m.any  characters  peculiar  to 
itself  must  an  animal  or  plant  possess  to  justify  its  ele- 
vation to  specific  rank,  but :  how  have  these  characters 
arisen,  or  how  can  they  arise  ?^ 

In  other  w^ords :  the  mutation  and  the  actual  process 

of  mutating  must  become  the  object   of   investigation. 

And  if  we  once  discover  the  nature  of  this  process,  not 

only  will  our  insight  into  the  actual  relationship  of  living 

organisms  become  much  deeper,  but  w^e  may  even  hope 

that  we  may  be  able  to  gain  some  measure  of  control  over 

the  formation  of  species.     If  the  breeder  has  obtained 

control  over  variability  why  should  he  not  obtain  it  over 

mutation   as  well  ? 

^  "These  factors  are  the  units  with  which  the  science  of  heredity 
has  to  deal."  Intracell.  Pangenesis,  p.  9.  For  their  association  in 
groups  see  pp.  21-22  and  ZZ- 


Mutations  in  Cultivation.  187 

It  is  clear  that  we  can  only  advance  by  very  small 
steps  dealing  at  each  step  v^ith  a  single  mutation.  But 
even  single  mutations  may  be  of  enormous  importance 
in  horticulture  or  agriculture.  Much  that  now  seems 
unattainable  may  come  within  our  power  if  only  we  can 
obtain  some  insight  into  the  fundamental  principles  in- 
volved in  mutation.  There  lies  here  a  wide  field  of  work 
the  results  of  which  will  be  as  important  to  the  biologist 
as  to  the  practical  man. 

§  25.    MUTATIONS   IN   CULTIVATION. 

In  a  preceding  section  {%  23)  I  endeavored  to  show 
that  man}^  of  the  elementary  species  which  exist  in  a 
state  of  cultivation  had  arisen  before  they  were  intro- 
duced into  it.  But  it  does  not  follow  that  this  is  always 
the  case  as  Jordan,  Kerner  and  others  believe. 

On  the  contrary  in  many  cases  there  is  historical 
evidence  which  at  least  makes  it  highly  probable  that 
mutations  occur  in  the  garden  and  the  field  no  less  than 
in  the  wild  state.  But  it  usually  happens  that  the  new 
form  is  not  seen  until  it  is  alreadv  established;  how, 
when  and  where  it  arose  cannot  be  discovered,  or  at 
most  only  with  a  small  degree  of  certainty. 

According  to  the  theory  of  selection  the  origin  of  a 
new  form  is  a  gradual  process  which  we  can  observe 
whilst  it  is  taking  place.  But  the  evidence  at  our  dis- 
posal does  not  support  this  theory.  It  is  true  that  forms 
wdiich  have  arisen  suddenly  exhibit  a  high  degree  of 
fluctuating  variability  and  so  give  the  selector  the  oppor- 
tunity of  intensifying  the  new  character.  But  that  is 
a  very  different  matter  from  the  gradual  origin  of  the 
new  character. 


188  The  Origin  of  Species  by  Mutation. 

Good  examples  of  mutations  can  be  found  in  agri- 
cultural and  horticultural  literature.  But  before  I  give 
a  selection  of  them  I  must  point  out  how  clearly  the  dis- 
tinction between  races  and  subspecies  is  appreciated  by 
practical  authors.  Prof.  Kurt  von  Rumker  in  his  often 
quoted  Introduction  to  the  Breeding  of  Cereals  divides 
his  treatment  of  methodical  selection  into  two  parts. 
One  of  them  deals  with  selection  w^ith  a  view  to  improve- 
ment, the  other  with  selection  with  a  view  to  the  origin 
of  new  forms. ^  The  object  of  the  former,  he  says,  is 
to  fix  characters  already  present,  to  stamp  them  so  to 
speak,  and  to  intensify  desirable  qualities. 

New  forms,  however,  arise  when  the  changes  "do 
not  consist  merely  in  continuous  improvement  along  one 
line  but  in  the  production  of  new  qualities  as  lateral  off- 
shoots." Such  changes  occur  now  and  then  in  our  fields 
and  are  known  as  spontaneous  variations.  ''Nothing  is 
yet  known  with  certainty  about  the  origin  of  such  spon- 
taneous variation  and  still  less  about  the  causes  of  their 
origin."     All  that  we  know  is  that  they  are  inherited. 

After  these  quotations  from  Von  Rumker  the  com- 
mon phrase  "the  production  of  new  forms"  will  sound, 
to  say  the  least,  exaggerated :  we  should  be  nearer  the 
mark  if  we  spoke  of  the  search  for  new  forms  (and  of 
their  subsequent  improvement,  in  the  usual  sense  of  the 
term). 

The  awnless  form  of  Beseler^s  Anderbecker  Oats 
is  a  very  famous  example  of  a  form  which  was  found 
ready  to  hand  in  the  fields. 

I  propose  to  give  now  a  series  of  further  examples. 
In  almost  all  the  cases  the  new  sorts  have  come  absolutely 
true  to  seed  from  the  very  beginning  when  the  possibility 

*  P.  XIV,  and  56  and  83. 


Mutations  in  Cultivation.  189 

of  crossing  has  been  rigidly  excluded.  Sometimes  the 
new  character  appears  very  slightly  developed  in  the 
first  instance  as  in  the  case  of  ''double"  flowers.  In  such 
cases  the  characters  have  to  be  improved  by  selection. 
In  some  the  variation  appears  once  and  for  all,  in  others 
it  continually  reappears.  It  is  well  known  that  every 
breeder  should  look  anxiously  for  possible  novelties ;  but 
when  he  has  found  one,  it  depends  on  him  and  on  him 
alone  whether  it  attains  its  full  beauty. 

The  origin  of  the  new  form  is  emphatically  due  to 
chance  and  not  to  the  skill  of  the  breeder,  as  it  is  in  the 
improvement  of  races. 

Chelidonium  laciniatum  Miller,  a  subspecies  of  Cheli- 
doniuni  ma  jus,  is  one  of  the  most  beautiful  examples 
because  more  is  known  about  its  origin  than  about  that 
of  almost  any  other  plant,  thanks  to  the  painstaking  in- 
quiries of  E.  RozE.i   j^g  gives  the  following  history  of  it. 

About  the  year  1590,  Sprenger,  an  apothecary  in 
Heidelberg,  found  in  the  garden  where  he  grew  plants 
for  his  business  (amongst  which  was  Chel.  majns),  a 
new  form  of  Chelidonium  which  dififered  from  C.  majus 
in  the  possession  of  deeply  cut  leaves  and  petals.  He 
called  it  Chelidonia  major  foliis  et  floribns  incisis  and 
sent  some  examples  to  Jean  Bauhin,  Gaspard  Bauhin. 
Clusius,  Plater  and  other  well-known  botanists  of  his 
time.  All  of  them  declared  that  the  plant  was  unknown 
to  them  and  new.  It  had  never  been  found  wild  before, 
nor  has  it  been  found  since ;  although  from  time  to  time 
it  has  escaped  from  gardens.  It  comes  absolutely  true 
from  seed,  has  maintained  itself  till  the  present  day  and 
is  very  generally  grown  in  Botanical  gardens.     Miller, 

^  E.  RozE,  Le  "Chelidonium  laciniatum"  Miller,  Journal  de  Bo- 
tanique,  1895,  Nos.  16-18. 


190 


The  Origin  of  Species  by  Mutation. 


RozE  and  many  others  have  tested  its  constancy  by  cul- 
tures extending  over  many  years  and  have  observed  no 
reversion  to  C.  majus.  I  have  repeated  the  experiments 
with  the  same  result. 

We  may  conclude  therefore  that  C.  laciniatum  arose 
about  the  year  1590.  Unfortunately  Sprenger  does  not 
say  v^hence  the  seeds  came  which  gave  rise  to  it ;  whether 


Fig.  36.    Chclidonium  laciniatum.     A  flower  of  it  to  the 
left.     Below  a  flower  of  C.  majus. 


from  seed  saved  by  himself  from  C.  majus  or  from  some 
other  source.  The  former  is  the  more  probable  since 
otherwise  he  would  have  known  from  whence  he  had 
obtained  it. 

Transitions  between  the  two  species  in  question  do 
not  occur  to-day  any  more  than  they  did  in  Sprenger^s 


Mutations  in  Cultivation. 


191 


time.    We  may  presume  therefore  that  the  younger  form 
arose  suddenly  from  the  older  one. 

W.  T.  Thiselton  Dyer  has  described  a  series  of 
spontaneous  variations  of  Cyclamen  latifoliiim,  a  very 
interesting  species  from  the  fact  that  it  is  one  of  the 
very  few  garden  plants  with  which  crossing  had  not  yet 
succeeded.^  The  supposition  of  a  hybrid  origin  of  its  sub- 
species is  therefore  excluded.  A  form  with  horizontally 
projecting  petals  and  an- 
other with  hairy  struc- 
tures in  its  flowers,  re- 
minding one  of  similar 
structures  in  the  flower 
of  the  Iris,  have  been  de- 
scribed. The  first  form 
has  arisen  manv  times ;  it 
was  at  first  thrown  away 
as  unsuitable  for  cultiva- 
tion, but  has  since  been 
put  on  the  market.  The 
incised  petals  also  have 
arisen  several  times,  for 
example  in  1827,  when 
they  were  described  in  the 
Botanical  Register,  but 
were  subsequently  lost. 
Since  1850  they  have  appeared  ni  several  nurser}-  gar- 
dens. The  hairy  structures  suddenly  appeared  in  1890  in 
the  nursery  of  Messrs.  Hugh  Low  &  Co.,  although  in  a 
veiy  rudimentary  form.  They  were  greatly  improved 
by  repeated  selection,  and  after  a  few  years  put  on  the 


Fig.  38.    Chelidonium  ma  jus. 


^W.  T.  Thiselton  Dyer.  The  Cultured  Evolution  of  Cyclamen 
Latifolium.     Proceed.  Roy.  Soc,  Vol.  LXI,  No.  371,  p.  i35- 


192  The  Origin  of  Species  by  Mutation. 

market.  They  also  appeared  in  France  as  early  as  1885; 
but  there  they  were  not  cultivated  further.  They  exist 
both  in  the  red  and  in  the  white  variety. 

Strawberries  without  runners  belong  to  the  species 
Fragavia  alpina  and  are  known  under  the  name  of  Gail- 
i^ON-strawbcrncs.^  Forms  are  known  both  with  red  and 
with  white  fruits.^  The  history  of  their  origin  is  re- 
corded by  P.  P.  A.  De  Vilmorin  in  the  Bon  Jardinier.^ 
He  found  a  single  individual  bearing  this  character  in 
a  crop  of  the  ordinary  Fragaria  alpina.  The  seeds  of 
this  individual  gave  rise  solely  to  plants  without  runners : 
the  new  sort  was  absolutely  constant  from  the  beginning. 

The  cauliflower  and  Kohl-Rabi  were  raised  from  iso- 
lated monstrosities  of  Brassica  olcracca.^  The  Chou  de 
Milan  dcs  Vert  us  likewise  arose  spontaneously  from  an-' 
other  sort  of  cabbage  and  soon  became  one  of  the  most 
popular  vegetables  in  the  Paris  market.^  Merctirialis 
annua  laciniata  was  discovered  in  1719  by  Marchant 
as  a  new  form ;  since  that  time  it  has  come  true  from 
seed.^    That  is  the  last  of  these  examples  I  shall  refer  to. 

Some  species  have  appeared  twice,  or  even  more 
often,  in  localities  widely  distant  from  one  another  and 
under  circumstances  which  almost  completely  exclude  the 
])ossibility  of  a  common  origin.  I  may  quote  the  example 
of  the  copper  beech,  to  which  Prof.  J.  Jaggi  has  devoted 
an  exhaustive  historical  monograph."^     Three   localities 

^  See  Fig.  y  on  page  34. 

■"  Vilmorin  Andrieux  et  Cie.,  Les  plantes  potageres,  p.  222. 

^L.  De  Vilmorin,,  L' amelioration  des  plantes  par  le  semis,  2d  ed., 
p.  48. 

*A.  P.  De  Candolle,  Transact,  hortic.  Soc,  5,  p.  i,  quoted  in 
Hofmeister,  Allgemeine  Morpliologie,  p.  565. 

"  Vilmorin,  L'amelioration,  he.  eit.,  p.  ig. 

^GoDRox,  De  I'Espeee.  1,  p.  160. 

•  J.  Jaggi,  Die  Blutbuche  su  Biich  am  Irchcl,  Zurich,  1893. 


Mutatiuns  in  Cultivation 


193 


for  it  are  known.  The  Stammberg  near  Buch  am  I  rebel 
in  tbe  Zurich  Canton;  a  wood  near  Sondersbausen  in 
Thuringia;^  a  wood  above  Castellano  near  Roveredo  in 
the  southern  Tyrol  The  first  locabty  was  known  as 
early  as  the  17tb  century;  the  second  in  tbe  second  half 
of  the  18th  century;  the  third  only  at  the  beginning  of 
the  19th.  In  the  same  way  Fragaria  monophylla  (Fig. 
38)  was  found  by  Fries  in  the  neighborhood  of  Skaru- 
gata  in  Lapland ;  then  it  arose  in  a  garden  near  Versailles 
about  1761  and  is  now  to  be  found  in  many  botanical 


Fig.  38.  Fragaria  vesca  monophylla.  a,  two  leaves;  /',  a 
young  plant  on  a  runner  with  single,  double  and  triple 
leaves — a  case  of  atavism. 

gardens.^  Fagus  sylvatica  aspleniifolia  was  found  in  a 
wood  in  Lippe-Detmold  and  in  the  neighborhood  of 
Paris.^  Alniis  glutinosa  laciniafa  (Fig.  39)  and  Bctula 
alba  laciniata  are  found  wild  in  Sweden  and  Lapland.^ 

*  l\Ir.  ^.,  DoRiNG  in  Sondershaiisen  informed  me,  that  this  tree  is 
still  living;  its  foliage  as  well  as  that  of  its  offspring  is,  however, 
only  of  a  pale  red.     (Note  of  1908). 

"Braun,  Abh.  k.  Acad.,  Berlin,  1859,  p.  113;  Hofmeister,  Allg- 
Morphologie,  p.  557  and  571;  Bot.  Zeitung,  1878,  p.  283;  Alph.  de 
Candolle,  Geographie  botanique,  II,  p.  1081. 

'  E.  Faivre,  L'espece,  p.  44;  the  former  statement  is  from  Braun, 
Verjilngung. 

*  Braun^  loc.  cit.,  p.  332. 


194 


The  Origin  of  Species  by  Mutation. 


In  the  nursery  gardens  the  same  novehy  often  appears 
simultaneously  in  different  places;  as  for  example  Age- 
ratiim  mexicaniim  naniim  luteum  which  arose  about  1892 
in  both  Paris  and  Erfurt.^ 

There  is  a  series  of  varieties  on  the  market,  of  the 
most  diverse  botanical  species,  of  which  it  can  be  said 
that  it  would  be  practically  impossible  for  them  to  grow 
wild.   They  have  often  been  brought  forward  as  evidence 


Fig.  39.  a,  Alnus  gliitinosa  lacl- 
niata  with  fruits ;  b,  leaf  of 
Alnus  slutinosa. 


Fig.  40.  Rammculus  acris  pcia- 
lomana,  a  form  which  has  be- 
come completely  sterile  by 
profuse   petal   formation. 

From   a   plant    found   in   a 
meadow. 


for  the  view  that  varieties  arise  suddenly  in  cultivation 
by  so-called  spontaneous  variation  or  mutation.  I  recall 
those  fruits  which  cannot  dehisce  as  Papaver  somni- 
feruni  inapertmn  and  Linum  usitatissinium  (L.  crepitans 
is  the  only  subspecies  which  open  its  fruits  so  as  to  scatter 
the  seeds).  Then  there  are  the  large  and  heavy  seeds  of 
cereals  and  some  Legwninosae  but  especially  of  maize 

^  I  was  told  this  by  Mr.  Otto  Putz.,  a  nurseryman  in  Erfurt. 


Mutations  in  CultivatioH. 


195 


whose  seeds  seem  to  have  no  means  of 
becoming  distributed.  Lastly  there  are 
the  sterile  varieties;  Currants  (Corin- 
thian grapes),  Bananas,  many  sorts  of 
apples  and  pears,  astrakhan  grapes, 
some  strawberries,  the  green  rose,  the 
green  Pelargonium  sonale  and  green 
Dahlias  (of  which  I  have  cultivated 
two  different  sorts,  one  with  elongated 
and  the  other  with  ordinary  flat  flower- 
heads).  Ranunciihis  acris  and  Caltlia 
palustris  which  have  become  sterile  by 
petalomany  (Fig.  40)  and  many  other 
examples  of  this  kind  of  doubling;^ 
then  there  is  the  sterile  Maize  (Fig. 
41)  many  examples  of  which  have  ap- 
peared in  my  own  cultures  but  which, 
so  far  as  I  know,  does  not  seem  to 
have  been  noticed  elsewhere.^ 

The  great  majority  of  forms  which 
have  arisen  suddenly,  be  they  varieties 
or  subspecies,  come  absolutely  true 
from  seed;  that  is  to  say  every  single 
seed  gathered  reproduces  the  new  form 
when  sown,  provided  that  the  seed  pa- 
rent was  fertilized  w^ith  its  own  pollen, 
or  with  pollen  from  another  example 
of  the  same  form.  Constancy  is  one  of 
the   properties   of   elementary   species. 

^  K.  GoEBEL.  Pringsheim's  Jahrhiichcr  fiir 
wissensch.  Bot.,  Vol.  XVII,  p.  207. 

^  Over  stericle  Maisplanten,  Botan.  Jaarboek 

1889,  Table  V,  p.  141.     Steriele  Mais  als  erfelyk 

1890,  p.  109. 


Fig.  41.  Zca  Mays 
sterilis.  Three  un- 
branched  "pan- 
icles." a,  without 
bracts  ;  b  and  c. 
with  slight  bract 
formation  at  the 
tip. 

Dodonaea,  Vol.  I, 
ras,  ibid..  Vol.  y, 


196  The  Origin  of  Species  by  Mutation. 

Apparent  exceptions  to  this  rule  are  so  numerous  that  we 
might  be  inchned  to  doubt  its  universal  validity.  But  in 
most  cases  it  will  be  found  that  those  who  record  such 
exceptions  have  paid  no  regard  to  the  possibility  of  cross- 
fertilization  by  insects  or  by  the  wind.  Crossing  is  cer- 
tainly the  simplest  and  most  obvious  explanation  of  them. 
The  whole  subject  of  so-called  atavism  in  plants  demands 
a  careful  re-investigation,  for  most  of  what  passes  as 
atavism  in  the  nursery  and  private  gardens  is  nothing 
more  nor  less  than  the  result  of  accidental  crossing.  At 
least  so  my  researches  into  these  phenomena  lead  me  to 
believe. 

I  shall  however  return  to  this  subject  and  deal  with 
it  more  thoroughly  in  a  later  section ;  and  shall  confine 
myself  now  to  citing  some  of  the  more  important  in- 
stances of  constancy. 

The  complete  constancy  of  many  varieties  is  well 
known.  As  for  example  in  the  case  of  Matricaria  Cham- 
omilla  discoidea  and  the  corresponding  varieties  of  Bi- 
dens  tripartita  and  Senecio  Jacohaea.  Also  of  Datura 
tatula  ineruiis/  of  Ranuncidus  arvensis  iuermis,^  of  the 
peloric  varieties  of  Antirrhinum  majus,^  of  Nigella  sa- 
tiva  apetala,^  of  Ilex  Aqtd folium  with  yellow  berries,'* 
of  weeping  oaks  and  weeping  birches,^  of  red-leaved 
Bcrheris,'^  of  the  peloric  form  of  Corydalis  solida,^  of 
Hordeum  trifurcatum,  Rubus  fruticosus  laciniafus  be- 
sides countless  garden  plants  and  vegetables  (sugar  peas, 
thornless  spinach  and  so  forth). 

^  Botan.  Zeitung,   1873,  p.  687. 

*  Masters,  Vegetable  Teratology,  p.  227. 

^Hoffmann,  Botan.  Zeitung,  1881,  p.  410;  a  number  of  other 
examples  are  recorded  here. 

*  Darwin,  Variation  in  Animals  and  Plants,  II,  pp.  24,  26. 
^GoDRON,  Mem.  Acad.  Stanislas,  t868,  p.  3. 


Mutations  in  Cultivation.  197 

I  have  already  said  that  the  so-called  cases  of  atavism, 
brought  forward  as  evidence  against  this  constancy,  are 
really  cases  of  crossing.  The  copper  beech  illustrates 
this  well.  Its  distinguishing  character  is  reported  as  be- 
ing inherited  to  a  highly  variable  extent,  according  to 
the  locality  in  which  it  lives.  Sometimes  all  the  seeds 
come  true;  sometimes  only  20%.  But  as  the  trees  in 
question  grow  amongst  ordinary  beeches,  and  as  arti- 
ficial fertilization  is  of  course  out  of  the  question,  they 
must  usually  be  fertilized  by  pollen  from  the  surround- 
ing trees.  If  we  want  to  draw  any  conclusions  from 
the  posterity  of  a  copper  beech  w^e  must  confine  our  atten- 
tion to  properly  isolated  trees. 

In  conclusion  we  may  refer  to  the  familiar  fact  that 
in  cultivation  mutations  follow  on  one  another  so  that 
the  plant  gradually  becomes  separated  from  the  original 
form  by  an  increasing  number  of  characters;  which  is 
exactly  what,  in  all  probability,  occurs  in  nature.  The 
great  number  of  long  names  of  garden  plants  is  evidence 
of  this ;  as  for  example  Scabiosa  atropiirpurea  nana  pur- 
purea from  which  a  Forma  carnca  and  a  Forma  rosea 
have  subsequently  arisen ;  Calliopsis  tinctoria  pumila  pur- 
purea, Tagetes  potula  nana  with  dark  leaves,  and  another 
form  of  this  dwarf  with  bright  yellow  flowers  and  so 
forth.  The  succession  of  names  often  indicates  the  stages 
of  development  of  the  form  in  their  historical  sequence. 

Finally,  then,  we  may  say  that  a  gradual  origin  of 
elementary  species  has  not  yet  been  observed ;  but  that 
there  are  hosts  of  instances  in  which  new  ''species"  have 
arisen  suddenly  or  in  which  at  least  such  an  origin  is  in 
the  ver}^  highest  degree  probable.  Scarcely  ever  has  the 
new  form  been  isolated  immediately  it  appeared :  it  is 
usually  left  like  its  parents  to  pollination  by  insects.    So 


198  The  Origin  of  Species  by  Mutation. 

far  as  this  circumstance  allows  us  to  judge,  these  new 
species  are  as  a  rule  just  as  constant  as  the  older  so-called 
"good"  species. 

§  26.    THE  HYPOTHESIS   OF  INDISCRIMINATE 

MUTABILITY. 

The  chief  merit  of  Darwin's  theory  of  selection  was 
that  it  explained  the  adaptation  which  is  seen  on  all 
hands  in  organic  nature  on  purely  natural  principles  and 
without  the  aid  of  any  teleological  conception.  It  is  be- 
cause it  does  this  so  completely  that  the  theory  of  descent 
has  gained  such  universal  acceptance.  The  universal 
belief  in  the  kinship  of  living  forms,  in  its  turn  now 
makes  the  experimental  study  of  the  manner  in  which 
one  species  arises  from  another,  possible.  Nay,  it  chal- 
lenges us  to  such  an  inquiry.  How  the  species  which 
exist  at  the  present  time  arose  in  the  past  is  evidently  a 
historical  question  which  can  only  be  directly  answered 
in  a  very  few  cases.  But  the  determination  of  the  mode 
of  origin  of  species  must  soon  become  the  subject  of 
inquiry  just  like  any  other  physiological  process. 

According  to  the  Darwinian  principle,  species-form- 
ing variability^ — mutability — does  not  take  place  in  defi- 
nite directions.  According  to  that  theory,  deviations  take 
place  in  almost  every  direction  without  preference  for 
any  particular  one,  and  especially  without  preference  for 
that  direction  along  which  differentiation  happens  to  be 
proceeding.  Every  hypothesis  which  differs  from  Dar- 
win's in  this  respect  must  be  rejected  as  teleological  and 
unscientific. 

The  struggle  for  existence  chooses  from  among  the 
mutations  at  its  disposal  those  which  are  the  best  adapted 

^  Intracellular e  Pangenesis,  pp.  yZy  210,  etc. 


The  Hypothesis  of  Indiscriminate  Mutability.   199 

at  the  moment;  in  this  way  alone  can  their  survival  be 
explained. 

According  to  Wallace's  and  his  followers'  modi- 
fication of  the  theory  of  selection  that  process  concerns 
the  individuals  of  one  and  the  same  species  only.  Accord- 
ing to  the  theory  of  mutation,  however,  the  units  with 
which  selection  deals  are  the  species  themselves.  Some 
survive  and  extend  the  limits  of  their  distribution ;  others 
are  wiped  out ;  the  former  may  again  be  the  source  of  new 
species,  the  latter  vanish  and  leave  no  posterity.  The 
essential  idea  of  this  theory  may  be  expressed  by  saying 
that  by  natural  selection  species  are  not  created  but  elimi- 
nated. 

Wallace's  theory  of  selection  and  the  theory  of 
mutation — specializations  in  two  different  directions  of 
Darwin's  theory — both  have  to  account  for  evolution 
without  calling  in  the  aid  of  a  theory  of  variation  in  a 
definite  direction.  Wallace's  theory  obviously  does  this 
inasmuch  as  according  to  it  the  material  on  which  selec- 
tion operates  is  individual  variability ;  moreover  the  study 
of  this  variability  rewards  the  student  with  a  rich  harvest 
of  facts  which  might  afford  a  strong  support  for  this 
theory  were  there  not  other  reasons  for  rejecting  it. 

The  theory  of  mutation  is  in  this  respect  less  for- 
tunate. For  mutations  themselves  can  only  be  directly 
observed  in  a  very  few  cases ;  and  in  fewer  still  have  they 
been  properly  studied.  Mutations  are  naturally  much 
rarer  than  individual  variations,  which  every  animal  and 
plant  exhibits ;  they  do  not  lend  themselves  to  investiga- 
tion in  the  same  way  as  the  latter.  Nevertheless  they  can 
be  made  the  subject  of  research,  and  for  many  reasons 
they  ought  to  be  investigated  just  as  minutely  as  varia- 
tions have  been. 


200  The  Origin  of  Species  by  Mutation. 

One  of  the  greatest  faults  of  those  who  hold  the  cur- 
rent theories  of  selection  is  that  they  have  focussed  their 
attention  much  too  exclusively  on  the  phenomena  of  se- 
lection and  individual  variation  and  much  too  little  on 
mutations.  There  can  be  no  doubt  th^it  this  is  one  of  the 
chief  causes  of  the  depth  of  our  ignorance  of  the  facts 
of  mutation. 

This  circumstance  explains  how  it  is  that  we  can  do 
no  more  in  the  matter  of  testing  the  hypothesis  of  indis- 
criminate mutal^ility  by  the  facts  at  our  disposal,  than 
find  out  how  far  the  special  hypotheses  put  forward  by 
various  authors  are  in  harmony  with  fundamental  and 
undisputed  Darwinian  principles. 

Nor  is  this  task  an  easy  one.  The  question  is  ob- 
viously :  what  share  in  the  origin  of  the  larger  or  collec- 
tive species  is  to  be  ascribed  to  mutability  and  what  to 
the  natural  elimination  of  elementary  species.  Many 
authors  have  suggested  that  altered  conditions  of  life 
exert  a  direct  influence  on  animals  and  plants  in  such  a 
way  that  new  characters  are  developed  which  render  their 
possessors  better  fitted  to  their  new  environment.  The 
environment  has,  according  to  them,  the  power  of  directly 
evoking  in  the  organism  an  adaptive  response. 

But  this  assumption  seems  to  be  no  more  than  a 
begging  of  the  question  we  are  trying  to  answer.  Dar- 
w^in's  idea  was  that  mutability  took  place  in  all  directions 
and  that  the  most  favorable  mutations  were  preserved. 
And  this  view  of  the  matter  will,  it  seems  to  me,  remain 
the  simplest  and  most  probable  answer  to  the  question 
imtil  such  time  as  we  have  collected  sufficient  experi- 
mental evidence  to  decide  whether  this  mutability  exists 
or  not. 

We  must  now  discuss  in  some  detail  the  views  of  W. 


The  Hypothesis  of  Indiscriminate  Mutability.  201 

B.  Scott,  one  of  the  most  prominent  champions  of  the 
theory  of  mutation,  who,  however,  has  declared  against 
the  hypothesis  of  indiscriminate  mutability  on  paleonto- 
logical  grounds.  For  it  seems  to  me  that  this  hypothesis 
agrees  perfectly  well  with  the  facts  of  paleontology  and 
especially  with  those  wonderful  genealogical  series  which 
have  lately  been  discovered.  Unfavorable  species  may 
well  have  arisen  in  far  greater  numbers  than  we  should 
ever  imagine,  without  having  left  the  shghtest  trace  in 
geological  strata.  The  continuous  series  certainly  point 
to  selection  in  a  constant  direction  during  long  periods 
of  time,  but  by  no  means  do  they  in  my  opinion  demand 
a  theory  of  mutability  in  a  definite  direction ;  for  their 
explanation. 

A  closer  examination  of  Scott's  arguments  will  show 
how  far  my  view  is  justified.  Scott  asserts  that  those 
paleontological  series  which  are  well  knowni,  are  con- 
tinuous and  without  gaps ;  whereas  those  in  which  the 
gaps  are  many  are  just  those  which  are  imperfectly 
known.  This  incompleteness  is  due  either  to  the  absence 
of  individual  strata  from  certain  periods  or  to  the  fact 
that  it  has  not  yet  been  possible  to  examine  the  strata 
in  question,  properly.  But  where  the  series  of  strata  is 
continuous  and  without  gaps,  and  their  examination  thor- 
ough, the  genealogical  tree  has  also  proved  to  be  contin- 
uous and  without  gaps.  This  is  evident  in  the  case  of 
the  well-known  pedigree  of  the  horse,  in  those  of  many 
other  mammals,  of  Ammonites  and  so  forth. 

Such  series  always  possess  this  remarkable  feature : 
they  proceed,  so  to  speak,  in  a  straight  line.  Evolution 
makes  straight  for  its  goal  without  deviation,  swerving 


202  The  Origin  of  Species  by  Mutation. 

neither  to  the  right  nor  to  the  left  so  as  to  form  a  zig-zag 
line.-^ 

The  question  we  have  to  answer  now  is  how  can  such 
a  definite  and  apparently  predetermined  series  of  changes 
be  explained  by  natural  principles  and  especially  by  the 
principles  of  descent  enunciated  by  Darwin  ;  in  other 
words :  how  must  we  picture  mutability  and  natural  se- 
lection to  ourselves  in  order  to  gain  a  satisfactory  expla- 
nation of  these  series.  Two  ways  of  explaining  them 
are  possible. 

1.  iMutability  may  take  place  in  almost  all  directions; 
and  it  is  natural  selection  which  operates  in  one 
direction  during  long  geological  periods. 

2.  Mutability  takes  place  only  in  one  direction  and 
itself  determines  the  direction  of  change. 

The  former  obviously  represents  the  view  of  Dar- 
win ;  the  latter  that  of  Scott. 

In  the  first  place  it  must  be  remembered  that  when  we 
are  dealing  with  paleontological  facts  it  is  hardly  possible 
to  decide  between  mutability  and  selection,  and,  as  Scott 
has  remarked,  no  ''explanation"  can  ever  be  much  more 
than  a  guess. 

There  is  every  reason  for  supposing  that  in  the  gen- 
ealogy of  every  organism  numlDers  of  species  may  have 
arisen  but  have  never  multiplied  sufficiently  to  insure 
their  preservation  in  the  rocks,  and  have  disappeared 
without  leaving  behind  them  either  posterity  or  record. 
Paleontology  can  obviously  not  help  us  to  decide  as  to 
the  admissibility  of  such  a  theory.     Let  us  therefore  com- 

^  Weldon  regards  this  objection  to  the  theory  of  selection  the 
most  serious  of  all.  See  his  Presidential  Address :  On  the  Three 
Principal  Objections  which  Arc  Urged  Against  the  Theory  of  Nat- 
ural Selection,  8th  Sept.,  1898.  Brit."  Ass.  Adv.  Science,  Bristol,  1899, 
p.  887. 


The  Hypothesis  of  Iiidiscriininate  Mutability.  203 

pare  the  number  of  species  in  these  geological  series  with 
the  wealth  of  our  modern  collective  species  in  elementary 
types.  Can  there  be  any  question  that  this  richness  ex- 
isted at  all  times  in  spite  of  the  fact  that  there  is  no  geo- 
logical record  of  it?. 

We  will  again  refer  to  the  composite  species  Draba 
verna,  which  has  been  so  fully  elucidated  by  Jordan. 
Thuret,  De  Bary,  Rosen  and  others.  It  is  generally 
assumed  that  all  the  elementary  species  of  Draha  vcrna 
spring  from  a  single  original  form ;  yet  they  differ  from 
one  another  in  every  conceivable  direction.  They  must 
liave  arisen  as  mutations  from  this  form ;  which  must 
therefore  have  produced  them  in  all  directions  and  not 
in  one  particular  one.  They  afford  sufficient  material 
for  natural  selection ;  whatever  view  of  it  we  hold. 

Supposing  that  the  ancestors  of  the  horse  exhibited 
a  similar  indiscriminate  mutability,  what  chance  would 
there  be  of  their  preservation  in  the  fossil  state?  This 
question  is  a  difficult  one  to  answer  and  calls  for  further 
treatment.  The  present  number  of  elementary  types  be- 
longing to  a  species  is  no  measure  of  the  number  of 
mutations  it  may  have  produced  since  its  origin.  By 
far  the  greater  number  of  mutations  presumably  perish, 
nipped  in  the  bud  by  natural  selection.  Other  forms 
may  continue  for  one  or  two  years,  but  after  a  time,  they 
too  disappear.  It  is  only  a  very  few  which  ultimately 
come  to  take  part  in  the  great  struggle  for  existence. 

Much  that  appears,  must  forthwith  disappear.  Even 
between  the  male  and  female  individuals  of  one  and  the 
same  species  there  is  often  a  strong  competition  whicli 
may  result  in  a  permanent  alteration  of  their  numerical 
proportions.  As  a  rule  male  plants  are  more  delicate, 
and  we  find  quite  regularly  that  in  unfavoral)le  positions 


204  The  Origin  of  Species  by  Mutation. 

the  females  have  increased  in  number  in  proportion  to 
the  males.  This  was  observed  by  Hoffmann  on  Spi- 
nacia,  Rvunex  and  LycJinis,  and  by  others  on  many  other 
species.  In  Matthiola  incana  the  strongest  seeds  give 
double-flowered  individuals  but  the  proportions  of  such 
depend  on  the  conditions  in  which  they  are  cultivated ; 
when  seeds  are  gathered  in  the  open  they  do  not  exceed 
50%,  when  sown  in  puts  they  attain  60  and  sometimes 
70%. 

It  seems  to  me  therefore  to  be  a  warrantable  assump- 
tion that  in  geological  times  many  newly  arisen  forms 
were  promptly  anniliilated  and  have  left  no  trace. 

If  the  hypothesis  of  mutability  in  one  direction  ren- 
ders the  theory  of  a  selection  operating  in  a  constant 
direction  superfluous,  then  we  must  regard  mutations 
as  in  a  very  high  degree  limited.  Only  those  species, 
whose  remains  have  been  found  in  paleontological  strata 
could  have  arisen  by  it ;  and  strictly  speaking  only  those 
wliich  lav  in  the  direct  line  of  descent.  All  lateral 
branches  which  have  died  without  posterity  point  to  a 
selection  operating  continually  in  the  direction  of  the 
main  line  of  descent.  It  seems  to  me  that  the  more  we 
consider  Scott's  view  in  detail  the  more  do  the  differ- 
ences between  him  and  Darwin  tend  to  disappear. 

The  question  how  far  the  theory  that  selection  may 
have  operated  in  one  direction  during  long  periods  of 
time  is  justified  lies  outside  the  scope  of  this  book :  but 
it  will  be  admitted  first,  that  it  has  never  been  proved  to 
be  false,  and  secondly,  that  this  theory  has  at  least  as  much 
justification  as  that  of  mutability  in  one  direction. 

In  short:  The  mutation  theory  demands  that  organ- 
isms should  exhibit  mutability  in  almost  all  directions. 
The  facts  of  paleontology  and  classification  are  in  accord 


The  Hypothesis  of  Periodic  Mutability.  205 

with  this  theory.  And  the  fact  that  ordinary  or  collective 
species  consist  of  groups  of  elementary  species  whose 
characters  may  differ  in  every  conceivable  zvay  empha- 
sises the  existence  of  indiscriminate  mutability. 


§  27.     THE   HYPOTHESIS   OF   PERIODIC   MUTABILITY. 

Tlie  constancy  of  species  is  a  demonstrated  fact ; 
their  transmutabihty  is  still  a  matter  of  theory.  This 
is  the  old  objection  against  the  theory  of  descent.  La- 
marck, Darwin  and  Wallace  met  this  difficulty  by 
assuming  that  the  immutability  was  only  apparent  and 
was  due  to  the  fact  that  the  changes  are  so  slow  that  in 
the  short  time  during  which  we  are  able  to  observe  them 
they  can  not  be  detected. 

This  however  is  merely  an  assumption,  as  I  have  al- 
ready shown.  No  one  doubts  that  many  species  have 
undergone  vast  changes  during  the  course  of  centuries ; 
but  no  one  knows  whether  they  have  taken  place  grad- 
ually or  by  leaps  and  bounds. 

The  contrary  supposition  that  species  can  remain  ab- 
solutely unchanged  during  long  periods  of  time  but  under 
certain  circumstances  begin  to  produce  new  forms  seems 
to  me  at  least  equally  justified.  The  ancestors  of  species 
that  exist  to-day  have  on  this  theory  passed  through  im- 
mutal)le  and  mutable  periods :  the  division  of  the  large 
species  into  elementary  species  would  be  the  result  of  the 
last  or  of  some  of  the  last  periods  of  mutability.^ 

We  repeatedly  find  the  idea  of  a  periodic  transmuta- 
tion of  species  expressed  in  Darw^in's  works.     "Changed 

^  KoLLMANN  remarks  on  this  subject :  'Tn  no  species  of  animal 
or  plant  is  this  process — the  formation  of  new  races — a  perpetual 
one  but  is  confined  to  certain  periods.  If  this  were  not  the  case  we 
should  have  only  changing  forms   and   always  new   species   instead 


206  The  Origin  of  Species  by  Miitaiioji. 

conditions  of  life"  are  the  chief  causes  of  this  transmu- 
tation, and  Darwin  cannot  have  imagined  the  environ- 
ment to  have  been  perpetually  changing.  Moreover  Dar- 
win often  refers  to  the  fact  that  a  plant  exhibits  little 
variability  during  the  first  few  years  after  it  has  been 
brought  into  cultivation  but  after  3  or  5  years  begins  to 
give  rise  to  new  forms.  Even  if  the  explanation  of  this 
phenomenon  should  turn  out  to  be  different  from  that 
given  by  Darwin,  the  fact  that  he  insists  so  strongly 
upon  it  shows  at  any  rate  that  the  idea  of  periods  of 
greater  and  of  less  mutability  was  present  in  his  mind.-^ 
As  the  cause  of  these  periods,  Darwin  believed  that  ex- 
ternal influences  must  act  for  many  generations  before 
they  can  induce  any  change  of  this  kind. 

But  if  mutability  is  a  periodical  phenomenon  we  get 
round  the  difficulty  of  having  to  suppose  that  mutations 
should  appear  equall}^  at  all  times;  and  we  are  also  in  a 
position  to  account  for  the  apparent  periodicity  in  evo- 
lution. The  existence  of  long  intervals  of  time  during 
which  characters  remain  unaltered  is,  at  any  rate  in  the 
case  of  a  great  many  species,  a  matter  of  tolerable  cer- 
tainty. The  frequent,  although  not  universal,  existence  of 
the  same  elementary  species  in  localities  which  have  been 
separated  for  centuries  points  decisively  in  this  direction. 

Moritz  Wagner's  famous  theory  of  migration  is 
based  on  the  same  fundamental  idea.-  We  have  no  rea- 
son to  expect  mutability  so  long  as  its  external  causes 
are  absent.     So  long,  that  is  to  say,  as  the  climatic,  phys- 

of  the  constant  forms  which  actually  exist."  Correspondenzhlatt  d.  d. 
Ges.  f.  Anthropologie,  Vol.  31,  No.  i,  p.  3,  Jan.  1900. 

^  "I  do  believe  that  natuval  selection  will  generally  act  very 
slozvh',  only  at  long  intervals  of  time.'"  (Darwin,  Origin,  6th  ed., 
p.  850 

"Wagner^  Das  Migrationsgesets  der  Organismen. 


Mutation  Within  Mutation  Periods.  207 

ical  and  biological  environment  remains  the  same  we 
must  suppose  that  the  species  will  not  change.  But  if 
the  plant  extends  its  range,  or  if  those  with  whom  it  com- 
petes for  the  means  of  subsistence,  change  in  any  way, 
the  opportunity  for  the  appearance  of  mutations  is  at 
once  given.  Either  of  these  occurrences  might  result  in 
a  shorter  or  longer  time  in  a  rapid  and  considerable  in- 
crease in  the  number  of  individuals  and  this  might  be  the 
cause  of  the  appearance  of  mutations  on  the  scene.  For 
a  rapid  multiplication  of  this  kind  presupposes  the  germi- 
nation of  such  seeds  as  under  ordinary  circumstances 
either  w^ould  not  have  germinated  at  all,  or  would  have 
come  to  nought.  This  might  be  the  case  for  example 
with  seeds  of  weak  lateral  branches,  of  the  tips  of  in- 
florescences or  of  flowers  from  accessory  buds  and  so 
forth. 

But  these  are  after  all  only  suggestions;  and  I  feel 
strongly  that  we  ought  to  make  this  matter  a  subject 
for  experimental  inquiry;  to  look  for  species  which  hap- 
pen to  be  going  through  a  period  of  mutation  and  still 
more  to  discover  what  are  the  factors  which  will  enable 
us  to  induce  such  a  period  in  a  species  at  will.  We  have 
a  doctrine  of  descent  resting  on  a  morphological  founda- 
tion. The  time  has  come  to  erect  one  on  an  experimental 
basis.  y/ 

§  28.    THE  PHENOMENON  OF  MUTATION  WITHIN  THE 
LIMITS  OF  THE  MUTATION  PERIODS. 

Observations  on  periods  of  mutation  have  not  yet 
been  made.  On  the  other  hand  many  attempts  based 
on  a  priori  considerations  have  been  made  to  discover 
what  the  phenomenon  of  mutation  may  be  expected  to 
be  like. 


208  The  Origin  of  Species  by  Mutation. 

Two  theses,  which  help  to  remove  many  difficulties 
standing  in  the  way  of  the  mutation  theory,  have  been 
put  forward : 

1.  The  assumption  that  the  new  form  or  species  does 
not  arise  merely  once  from  the  parent  species  but, 
while  the  period  lasts,  a  great  many  times  and  with 
some  degree  of  regularity. 

2.  The  possibility  of  the  appearance  of  useless  or 
even  harmful  specific  characters — whose  existence 
is  not  compatible  with  the  ordinary  theory  of  selec- 
tion. 

The  object  of  these  considerations  was  to  show  that 
newly  arisen  forms  could  increase  sufficiently  to  enter 
the  struggle  for  existence  with  at  any  rate  a  fair  prospect 
of  success,  without  the  help  of  natural  selection.  But 
the  fact  that  the  actual  behavior  of  new  forms  when  they 
arose  was  insufficiently  known  and  that  arguments  there- 
fore could  not  start  from  a  posteriori  premises  had  the 
result  that  this  subject  received  little  attention.  Gulick 
and  Delboeuf  are  the  two  chief  writers  who  have  de- 
voted themselves  to  this  aspect  of  the  question. 

Gulick's  generalization  was:  A^i  initial  tendency 
due  to  accidental  variation  can  increase  and  develop  in 
succeeding  generations,  zvithout  reference  to  the  advan- 
tage of  the  species.  He  is  referring  not  to  an  extreme 
variant  of  individual  variation  but  to  a  mutation;  and 
moreover  to  one  on  which  natural  selection,  at  first  at 
any  rate,  has  no  effect.^ 

J.  Delboeuf  is  concerned  to  show  how  the  final  usur- 
pation, by  the  transmuted  forms,  of  the  space  and  means 
of  subsistence  which  supported  the  original   type   is  a 

*  See  Journ.  Linn.  Soc.  Zool.,  Vol.  XI,  p.  496  and  Vol.  XX  (iSSS") 
p.  215. 


Mutation  Within  Mutation  Periods.  209 

necessary  consequence  of  the  continuation  of  the  cause, 
which  gave  rise  to  the  first  deviation,  however  shght  it 
may  have  been.^ 

A  sharp  distinction  between  the  selection  and  the 
mutation  theory  was  not  drawn  at  the  time  when  Del- 
BOEUF  was  writing,  so  that  his  attention  was  directed 
indiscriminately  to  both  of  them.  I  shall  consider  the 
application  of  Delboeuf^s  thesis  to  the  latter  only.  And 
I  shall  further  limit  my  analysis  to  the  consideration  of 
those  cases  in  which  the  new  form  is  immediately  con- 
stant, and  this,  as  we  saw  in  §  25,  is  almost  always  the 
case. 

Delboeuf  starts  with  the  supposition  that  a  mutation 
does  not  arise  only  once  but  is  given  off  e^•ery  genera- 
tion in  a  definite  although  perhaps  a  small  number  of 
individuals  for  just  so  long  as  the  cause  of  the  mutation 
continues.  He  further  supposes  that  the  new  form  can 
multiply  in  peace,  and  that  its  increase  is  neither  aided 
nor  hindered  by  the  struggle  for  existence.  Under  these 
conditions  the  new  form  must  always  increase  in  numl)cr 
of  individuals  in  relation  to  the  parent  form  with  a  speed 
which  will  vary  directly  with  the  percentage  of  mutating 
individuals  produced  in  each  generation.  From  a  knowl- 
edge of  this  percentage  one  could  calculate  the  number 
of  generations  it  would  take  for  the  new  form  to  equal 
the  old  one  in  number,  and  also  how  man}-  years  must 
elapse  before  the  new  form  entirely  replaces  its  pro- 
genitor. 

In  the  numerical  tables  of  Delboeuf's  paper  some 

of  the  more  important  cases  are  worked  out  in  detail. 

The  general  principle,  however,  is  quite  clear:  A   ncn' 

^J.  Delboeuf,  Ein  auf  die  Umzvandlungsthcoric  anzvendharcs 
mathcmatischcs  Gesets,  Kosmos,  1877-1878,  Jahrg.  i,  Bd.  II.  pp. 
105-127,  especially  p.  112. 


210  The  Origin  of  Species  by  Mutation. 

form  ixHtJwut  any  advantage  whatsoez'er  in  the  struggle 
for  existence  zvill  maintain  itself  provided  (1)  that  it 
is  sufficiently  vigorous  and  fertile  and  (2)  that  it  does 
not  arise  merely  once  but  repeatedly  during  a  long  period 
of  time.^ 

Delboeuf^s  generalization  has  received  little  atten- 
tion. Nevertheless  it  seems  to  me,  in  principle  and  in  the 
light  of  the  facts  of  mutation,  to  be  sound.  It  explains 
in  a  very  simple  way  the  existence  of  the  vast  number 
of  specific  characters  which  are  quite  useless  or  at  any 
rate  as  to  the  use  of  which  we  have  no  idea  at  all — as 
for  example  the  differences  between  the  oft-cited  species 
of  Draba  verna. 

According  to  the  commonly  accepted  theory  of  selec- 
tion onl}^  characters  advantageous  to  their  possessors 
should  arise;  according  to  the  theory  of  mutation  on  the 
other  hand  useless  and  even  disadvantageous  ones  may 
also  appear.  And  according  to  Delboeuf^s  view,  the 
latter  may  also  persist  through  long  intervals  of  time 
side  by  side  with  the  useful  variations.  The  premises 
from  which  he  starts  are  at  any  rate  warranted  by  actual 
experience. 

^  With  regard  to  the  probability  of  this  last  condition  I  refer  the 
reader  to  the  instances  in  §  25,  pp.  193-196,  and  to  the  repeated  ap- 
pearance of  sterile  maize  (in  my  experiments)  both  of  which  support 
this  view. 


VI.  CONCLUSIOX. 

1.  The  student  of  morphological  and  historical  evo- 
lution is  concerned  with  the  origin  of  the  Linnean  or  col- 
lective species,  genera,  families  and  larger  groups.  The 
student  of  experimental  evolution  is  concerned  with  the 
origin  of  elementary  species,  or  rather  with  the  origin 
of  specific  characters. 

2.  ''The  real  difficulty  of  Darwin's  theory  is  the 
transition  from  artificial  to  natural  selection"  (Paul 
Janet).  This  difficulty  can  only  be  surmounted  by  ad- 
mitting that  the  improvement  of  races  and  the  origin  of 
new  forms  are  really  entirely  different,  and  only  ap- 
])arently  similar,  processes. 

In  Darwin's  time  no  distinction  was  drawn  between 
these  tw^o  processes. 

3.  "No  two  individuals  in  a  generation  are  abso- 
lutely alike."  This  well-known  saying  refers  to  fluctu- 
ating variability  and  has  nothing  to  do  with  the  theory 
of  descent. 

4.  ''Species  have  arisen  by  natural  selection  resulting 
from  the  struggle  for  existence."  This  statement  also 
needs  some  explanation.  The  struggle  for  existence,  that 
is  to  say  the  competition  for  the  means  of  subsistence, 
may  refer  to  two  entirely  different  things.  On  the  one 
liand  the  struggle  takes  place  between  the  individuals  of 
one  and  the  same  elementary  species,  on  the  other  be- 

•  tween  the  various  species  themselves.     The  former  is  a 


212  Cofichision. 

struggle  between  fluctuations,  the  latter  between  muta- 
tions. In  the  former  case  those  that  survive  are  the  in- 
dividuals which  find  conditions  favorable  to  them — that 
is  to  say,  as  a  rule,  the  strongest  individuals.  It  is  by  this 
process  that  local  races  arise,  and  by  it  that  acclimatiza- 
tion is  rendered  possible.  If  the  new  conditions  of  life 
are  relaxed,  the  adapted  race  reverts  to  the  form  from 
which  it  sprang. 

The  natural  selection  of  newly  arisen  elementary  spe- 
cies in  the  struggle  for  existence  is  an  entirely  different 
matter.  They  arise  suddenly  and  without  any  obvious 
cause;  they  increase  and  multiply  because  the  new  char- 
acters are  inherited.  When  this  increase  leads  to  a 
struggle  for  existence  the  weaker  succumb  and  are  elim- 
inated. According  as  the  young  or  the  parent  form  is 
l)etter  fitted  to  the  environment  wmII  the  one  or  the  other 
of  them  survive.  Species  no  more  arise  as  the  result  of 
this  struggle  for  existence,  than  they  do  as  the  result  of 
the  struggle  between  the  variants  of  one  and  the  same 
type — though  for  different  reasons  in  the  two  cases.  In 
order  that  species  may  engage  in  competition  with  one 
another  it  is  evidently  an  essential  condition  that  they 
should  already  be  in  existence ;  the  struggle  only  decides 
which  of  them  shall  survive  and  which  shall  disappear. 

It  is  evident  moreover  that  this  ''elimination  of  spe- 
cies" must  have  weeded  out  many  more  than  it  has  pre- 
served. 

In  a  word,  from  the  standpoint  of  the  theory  of  muta- 
tion it  is  clear  that  the  role  played  by  natural  selection 
in  the  origin  of  species  is  a  destructive,  and  not  a  con- 
structive one. 

5.  Herbert  Spencer's  well-known  expression  :  ''The 
survival  of  the  fittest"  may  mean  one  of  two  things : 


Conclusion.  213 

either  ( 1 )  the  survival  of  the  most  favorable  individuals 
within  the  hmits  of  the  constant  species  or  in  the  forma- 
tion of  local  races  or  (2)  ''the  survival  of  the  fittest  spe- 
cies" as  the  basis  for  the  theory  of  descent.  The  two 
expressions  are  quite  independent  of  one  another  and 
refer  to  two  entirely  different  spheres  of  inquiry. 

6.  According  to  the  theory  of  mutation  species  have 
not  arisen  gradually  as  the  result  of  selection  operating 
for  hundreds,  or  thousands,  of  years  but  discontinuously 
by  sudden,  however  small,  changes. ''  In  contradistinction 
to  fluctuating  variations  which  are  merely  of  a  plus  or 
minus  character  the  changes  which  we  call  mutations  are 
given  off  in  almost  every  manner  of  new  direction.  They 
only  appear  from  time  to  time,  their  periodicity  being 
probably  due  to  perfectly  definite  but  hitherto  undis- 
covered causes. 

The  theory  of  the  inheritance  of  acquired  characters 
comes  under  the  heading  of  fluctuations.  Acquired  char- 
acters have  nothing  to  do  with  the  origin  of  species.  Nor 
can  the  theory  of  descent  be  applied  to  the  solution  of 
social  problems. 


PART  II. 

THE  ORIGIN  OF  ELEMENTARY  SPECIES  IN  THE 

GENUS    OENOTHERA. 


I.   THE  PEDIGREE   FAMILIES. 

§  I.    OENOTHERA  LAMARCKIANA,  A  MUTATING  PLANT. 

(plate  I.) 

The  chief  obstacle  in  the  way  of  getting  material  suit- 
able for  investigating  the  origin  of  species  is  our  complete 
ignorance  of  the  conditions  under  which  this  process 
takes  place.  In  order  to  obtain  this  material  I  started  in 
1886,  to  search  the  country  round  Amsterdam  for  spe- 
cies, exhibiting  such  monstrosities  or  other  peculiarities 
as  I  thought  would  suit  my  purpose.  As  a  result  of  my 
quest  I  brought  over  one  hundred  species  into  cultivation, 
but  only  one  of  these  turned  out  to  be  what  I  really 
wanted. 

From  this  I  conclude  that  most  of  the  species  in  this 
locality  are  passing  through  a  period  of  non-mutation, 
and  that  plants  which  happen  to  be  actually  passing 
through  a  mutable  phase  are  encountered  at  any  rate, 
relatively  rarely. 

The  plant  in  question  is  Oenothera  Lamarckiana, 
which  together  with  its  nearest  allies  O.  biennis  and  O. 
nitiricafa  have  been  introduced  into  Europe  from  Amer- 
ica. The  species  Lamarckiana  differs  from  the  others 
by  its  taller  growth,  by  its  much  larger  and  more  beauti- 
ful flowers,  by  the  fact  that  self-fertilization  rarely  oc- 
curs,  bv   its   different   leaves,    and   so    forth.  ^      O.    La- 

^  For  the  synonyms,  and  a  discussion  of  the  relationship  as  well 
as  for  a  more  detailed  account  of  its  origin  see  Sur  Vintroduction  dc 


218 


The  Pedigree  Fain  Hies. 


niarckiana  was  introduced  from  America  into  our  gar- 
dens, from  which  it  has  subsequently  escaped.  At  any 
rate  this  was  the  case  in  the  locahty  in  which  I  found  it. 
This  was  close  to  Hilversum  and  afforded  peculiarly 
favorable  circumstances  for  the  most  minute  investiga- 
tion. I  visited  the  place  during  the  summers  of  the  years 
1886-1888  almost  every  week,  and,  since  that  date  at  least 
once  or  twice  nearly  every  year.     The  plant  grev.'  in  a 


Fig.  42.  Oenothera  Lamarckiana.  A  flower  nearly  natural 
size.  One  of  the  petals  has  been  removed  to  show  the 
eight  stamens  with  the  pistil  and  its  stigma. 


disused  potato-field  to  wdiich  it  had  spread  from  a  neigh- 
boring park.  It  began  to  spread  in  about  the  year  1875. 
and  during  the  10  years  1875-1885  it  extended  over  about 
half  the  field.     In  the  succeeding  years  it  multiplied  still 

rOenothera  Lamarckiana  dans  les  Pays-Bas,  in  Nedcrlandsch  Kruid- 
kundig  Archief,  T.  VI,  4,  1895 ;  also  the  later  sections  of  this  Part. 


Oenothera  Lamarckiana,  a  Mutating  Plant.      219 

more  rapidly ;  until  the  field  was  finally  planted  witli 
forest  trees.  At  the  present  day  traces  of  the  plant  still 
exist. 

A  rapid  multiplication  of  this  kind  during  the  course 
of  a  relatively  short  period  of  time  has  often  been  con- 
sidered as  one  of  the  conditions  for  the  appearance  of  a 
mutable  period.  This  consideration  led  to  a  closer  inves- 
tigation on  the  spot,  which  confirmed  the  conclusion. 

The  plant  exhibited  a  high  degree  of  fluctuating  varia- 
bility in  all  its  organs  and  characters.  It  presented  also 
numerous  variations  of  another  kind,  of  which  I  shall 
only  mention  fasciation^  and  "pitcher"-like  malforma- 
tions.- Most  of  the  plants  w^ere  biennials,  but  many  were 
annuals ;  and  a  few  lived  three  years,  as  in  the  case  of  the 
beet. 

That  I  really  had  hit  upon  a  plant  in  a  mutable  period 
became  evident  from  the  discovery,  which  I  made  a  year 
later,  of  two  perfectly  definite  forms  which  were  imme- 
diately recognizable  as  two  new  elementary  species.  One 
of  them  was  a  short-styled  form:  0.  hrevistylis,  which 
at  first  seemed  to  be  exclusively  male,  but  later  proved 
to  have  the  power,  at  least  in  the  case  of  several  individ- 
uals, of  developing  small  capsules  with  a  few  fertile  seeds. 
The  other  was  a  smooth-leaved  form  with  much  prettier 
f,oliage  than  O.  Lamarckiana  and  remarkable  for  the 
fact  that  some  of  its  petals  are  smaller  than  those  of  the 
parent  type,  and  lack  the  emarginate  form  which  gives 
the  petals  of  Lamarckiana  their  cordate  character.  T 
call  this  form  O  laevifolia:^ 

^  Over  de  erfelykheid  der  fasciatien.  Kruidkundig  Jaarhock  Do- 
donaea,  1894,  P-  72.    Cf.  pp.  92-95. 

"  Over  de  erfelykheid  der  syniisen.    Ibid.,  p.  129.    Cf.  p.  165. 

'  Both  forms  are  described  and,  in  part,  illustrated  by  Prof. 
Julius  Pohl:  Ueber  Variationsweite  der  Oenothera  Lamarckiana,  in 


220  The  Pedigree  Faniilies.  , 

Both  0.  brez'istylis  and  0.  laevifolia  come  perfectly 
true  from  seed  as  will  be  shown  later  on.  They  differ 
from  O.  Lamarckiana  in  numerous  characters,  and  are 
therefore  to  be  considered  as  true  elementary  species. 

When  I  first  discovered  them  (1887)  they  were  rep- 
resented by  very  few  individuals.  Moreover  each  form 
occupied  a  particular  spot  on  the  field.  O.  brevistylis 
occurred  quite  close  to  the  base  from  which  the  Oeno- 
thera had  spread ;  O.  laevifolia  on  the  other  hand,  in  a 
small  group  of  10  to  12  plants,  some  of  which  were 
flowering  whilst  others  consisted  only  of  radical  leaves, 
in  a  part  of  the  field  which  had  not  up  to  that  time  been 
occupied  by  O.  Lamarckiana.  The  impression  produced 
was  that  all  these  plants  had  come  from  the  seeds  of  a 
single  mutant.  Since  that  time,  both  the  new  forms  have 
more  or  less  spread  over  the  field. 

I  could  find  neither  of  these  forms  in  the  herbaria  of 
Leiden,  Paris  or  Kew ;  nor  have  the3^  so  far  as  I  have 
been  able  to  discover,  been  described  from  other  local- 
ities. Whether  or  no  they  did  arise  in  my  locality  can 
of  course  no  longer  be  determined.  But  I  think  that  until 
proof  to  the  contrary  is  forthcoming  this  must  be  re- 
garded as  extremely  probable.  So  much  at  any  rate  is 
certain  that  the  discovery  of  these  two  species  increased 
my  hope  of  witnessing  the  origin  of  other  species  from 
the  same  stock — a  hope  which  was  soon  to  be  fulfilled. 

In  the  autumn  of  1886  I  brought  two  samples  from 
Hilversum  to  Amsterdam  for  cultivation  in  the  experi- 
mental garden.  One  lot  consisted  of  nine  particularly 
fine  rosettes  with  almost  fleshy  roots;  the  other,  of  the 
seed  from  a  quinquelocular  fruit  from  a  plant  growing 

Oesterr.  Botan.  Zeitschr.,  1895,  Nos.  5  and  6.     (O.  laevifolia  is  re- 
ferred to  there  as  O.  oxypetala) . 


The  Lamarckiana-Faniily.  221 

in  the  middle  of  the  field.  Lastly,  in  the  autumn  of  1887 
I  collected  the  seeds  of  O.  lacvifolia.  I  obtained  in  this 
way  three  groups  which,  in  conformity  with  the  prin- 
ciple of  nomenclature  adopted  by  growers  of  beets,  I  call 
families ;  and  these  I  continue  to  grow,  separately,  to  the 
present  day. 

From  these  three  families  and  their  numerous  lateral 
branches  I  have  derived  my  wdiole  culture,  which  has  em- 
braced several  thousands  of  individuals  almost  every 
year.  Latterly  several  hundreds  of  plants  have  been  arti- 
ficially fertilized  for  seed  purposes  every  year. 

Furthermore  I  have  imported  O.  hrcvistylis  direct 
from  Hilversum,  because  it  did  not  arise  in  mv  cultures. 
I  have  also  occasionally  made  collections  of  seed  in  the 
field  to  afi^ord  material  for  control  experiments. 

In  each  of  these  three  families  new  species  have  arisen 
in  my  garden ;  and  they  have  been  essentially  the  same  in 
the  three  groups.  I  shall  deal  with  them  separately :  first 
with  that  derived  from  the  rosettes,  the  progeny  of  which 
I  shall  call  the  LamarckiafiaA^xmXy.  Of  this  family  the 
main  trunk  (§2)  and  a  lateral  branch  (§5)  wnll  be  dealt 
with  separately,  for  the  sake  of  simplicity  of  treatment ; 
but  the  results  arrived  at  with  the  latter  agree,  in  their 
broad  features,  with  those  obtained  from  the  former. 

From  the  seeds  of  O.  lacvifolia  the  Lacvifolia-imn'iW 
(§6)  arose;  from  the  seeds  of  the  above-mentioned  fruit 
a  group  wdiich  I  shall  call  the  La/a- family. 

§   2.    THE   LAMARCKIANA-FAMILY. 

The  original  parents  of  this  family  were,  as  we  have 
already  seen,  moved  to  the  botanical  garden  in  Amster- 
dam in  the  autumn  of  1886.     They  flowered  in   1887, 


222  The  Pedigree  Families. 

bearing  large  blossoms  both  on  the  main  stem  and  on 
the  numerous  lateral  branches,  and  set  a  quantity  of  seed. 
They  were  grown  on  an  isolated  bed  and  considered  as 
the  first  generation. 

From  their  seeds  I  raised,  in  1888  and  1889,  a  second 
generation  which  flowered  on  the  same  isolated  bed.  I 
chose  six  of  the  strongest  to  gather  seeds  from.  The 
third  generation  was  mature  in  1891  ;  it  was  not  isolated, 
but  flowered  in  that  vear  before  the  other  cultures  of 
Oenothera  began  to  bloom;  some  days  before  this  hap- 
pened all  open  flowers  and  all  the  buds  were  removed. 

From  the  seeds  of  the  first  and  second  generation 
there  appeared,  besides  the  normal  plants,  three  hitherto 
unknown  forms :  O.  nanella  and  O  lata  in  some  numbers, 
and  a  single  example  of  O.  rnbrinervis. 

My  hope  had  been  fulfilled.  But  the  difficulties  of  the 
experiment  had  meanwhile  become  so  great  that  I  was 
ol)liged  to  give  it  up  for  a  time.  The  laezHfolia-ia.m{\y 
was  meanwhile  continued  and  experiments  in  methods 
of  cultivation,  manuring  and  artificial  fertilization  and 
so  forth  were  carried  out  on  a  large  scale.  The  result 
was  that  in  1895  I  was  able  to  take  the  Lamarckiana- 
family  up  again  with  results  which  far  exceeded  m\- 
highest  expectations,  as  a  glance  at  the  genealogical  tree 
on  page  224  will  show.  Since  that  time  I  have  manured 
my  plants  heavily,  isolated  any  mutating  individuals  as 
soon  as  they  could  be  recognized  as  such  and  have  then 
chosen  the  strongest  rosettes,  as  early  as  possible,  as 
seed-parents  for  the  next  generation.  I  have,  further, 
treated  my  plants  as  much  as  possible  as  annuals;  and 
have  always  chosen  those  which  were  to  produce  seed  for 
the  next  generation  in  the  main  line  from  among  these. 
So  that  from  1895  to  1899  I  always  had  one  generation 


The  Lamarckiana-Family.  223 

each  year.  Fertilization  was  always  artificial;  the  flow- 
ers set  plenty  of  seed  when  impregnated  with  their  own 
pollen.  The  visits  of  insects  were  precluded  by  the  use 
of  prepared  paper  bags.^  The  production  of  new  species 
has  not  in  the  least  suffered  from  all  these  precautions. 

I  shall  now  summarize  the  whole  history  of  this  fam- 
ily in  the  form  of  a  genealogical  tree  (p.  224),  including 
in  it  only  the  main  line  of  descent  and  the  individuals 
which  mutated  directly  from  it. 

The  table  shows  the  eight  generations  in  succession; 
the  first  1886-1887,  consists  of  the  nine  plants  collected 
in  the  field  at  Hilversum;  this  and  the  two  following 
generations  each  occupy  two  years.  I  did  not  sow  the 
seeds  which  I  harvested  in  1891  till  1895 ;  from  that  time 
on,  each  generation  occupies  only  a  year.  In  the  column 
over  which  O.  Lam.  is  written  are  given  the  approximate 
numbers  of  individuals  which  were  examined  either  as 
seedlings  or  as  grown  plants,  in  each  year.  These  num- 
bers do  not  refer  to  the  total  number  of  seeds  sown  or 
even  to  the  number  of  seedlings  that  came  up,  but  to 
plants  which  were  examined  separately. 

The  table  also  shows  the  number  of  plants  which 
mutated  in  each  generation,  so  far  as  they  could  be  rec- 
ognized with  certainty.  It  is  probable  that  these  numbers 
are  in  many  cases  too  small  because  I  had  not  nearly 
space  enough  to  grow  all  the  seedlings  separately  until 
they  had  so  far  grown  that  their  true  character  was  a 
matter  of  absolute  certainty.  They  had  as  a  rule  to  be 
examined  as  seedlings  and  it  is  probable  that  m  this  way 
many  cases  of  mutation  were  overlooked. 

I  have  only  recorded  the  more  important  mutations 

^''On  the  Use  of  Transparent  Paper  Bags  for  Artificial  Fertili- 
sation," in  Hybrid  Conference  Report ;  Journal  Royal  Horticultural 
Society,  Vol.  XXIV,  April  1900,  p.  266. 


224 


The  Pedigree  Families. 


OENOTHERA  LAMARCKIANA. 

A 

THE  LAMARCKIANA  FAMILY. 

I 

TABLE  SHOWING  THE  ORIGIN  OF  NEW  SPECIES  FROM  THE 

TYPE. 

(The  figures  refer  to  the  numbers  of  individuals.) 


GENERATIONS 


SPECIES 


gigas 


albida 


ob- 
longfa 


rubri- 
nervis 


Lam. 


na- 

nella 


lata 


scin- 
tillans 


VIII 


VII 


VI 


V 


IV 


III 


II 


8th  gen. 

1899 
(annual) 

7th  gen. 

1898 
(annual) 

6th  gen. 

1897 
(annual) 

5th  gen. 

1896 
(annual) 

4th  gen. 

1895 
(annual) 

3rd  gen. 

1890-91 

(biennial) 

2nd  gen. 

1888-89 

(biennial) 

1st  gen. 

1886-87 

Hilversum 

and 

Amsterdam 

(biennial) 


1        0         1700     21  1 


9        0         3000     11 


11         29        3         1800       9  5        1 


25        135       20         8000     49      142        6 


1        15       176        8       14000     60        73        1 


1       10000       3  3 


15000       5  5 


The  Lamarckiana-F amily .  225 

in  the  table :  others  have  arisen,  but  they  have  either  not 
flowered  or,  being  partially  sterile,  have  set  no  seed ;  or 
are  of  minor  importance  for  other  reasons.  As  examples 
of  such  we  may  just  mention  O.  sublinearis  and  0.  suh- 
ovata  and  two  or  three  allied  types,  which  could  not  be 
distinguished  with  certainty  because  they  bore  no  seed. 
From  others  as,  e.  g.,  O.  leptocarpa,  0.  elliptic  a,  and  O. 
seviilata  I  have  made  sowings  with  successful  results 
although  the  experiments  were  carried  out  on  a  small 
scale  (cf.  §§  16-20).  In  the  case  of  one  form,  O.  spathu- 
lata,  I  have  so  far  only  obtained  rosettes,  and  the  same 
is  true  of  other  forms  to  which  I  do  not  propose  to  give 
special  names. 

The  above-mentioned  0.  laevifolia  and  O.  hrevistylis, 
which  were  found  in  the  original  locality  never  appeared 
in  my  cultures. 

The  numbers  on  the  table  show  that  my  experiment 
dealt  in  seven  generations  with  about  50,000  plants  and 
that  of  these  over  800  mutated;  i.  e.,  about  1.5%,  a  figure 
which  must  for  many  reasons  be  regarded  rather  as  too 
small  than  too  large.  In  the  case  of  every  mutated  in- 
dividual it  is  certain  that  since  1886  its  ancestors  w^ere 
normal  0.  Lamar ckiana. 

Whether  this  was  the  case  with  the  earlier  ancestors 
is  obviously  now  beyond  the  range  of  proof,  but  it  mav 
be  assumed  to  have  been  so  with  a  great  degree  of  prob- 
ability because  of  the  extreme  rarity  of  forms  that 
showed  any  deviation  in  the  field  at  Hilversum. 


226  The  Pedigree  Families. 


§  3.    THE  MUTATIONS  IN  THE  LAMARCKIANA-FAMILY. 

I  shall  now  describe  the  mode  of  origin  and  the  more 
important  characters  of  the  seven  new  species  mentioned 
in  the  table. 

I.  O.  gigas.^  A  vigorous  plant  with  broad  leaves, 
large  flowers  and  short  fruits  and,  so  to  speak,  better  in 
habit  than  O.  Lamarckiana  in  every  respect.  It  has  the  ap- 
pearance of  being  just  as  well  fitted  for  the  struggle  for 
existence  as  any  species  of  the  genus  to  which  it  belongs. 

Even  the  radical  leaves  of  quite  young  plants  betray 
the  identity  of  the  new  type.  They  are  broad  with  a 
broad  base  which  passes  into  the  petiole  abruptly  instead 
of  gradually  as  in  the  case  of  Lamarckiana.  The  leaves 
that  appear  later  possess  this  character  in  a  less  degree, 
but  it  is  always  recognisable.  The  form  of  the  leaf  is 
moreover  very  much  more  variable  than  in  any  other 
form  of  the  subgenus  Onagra;  examples  with  very  nar- 
row and  others  with  very  broad  leaves  occur  in  quite 
small  groups  of  individuals. 

Its  stem  is  thicker  than,  though  about  the  same  height 

^  With  regard  to  the  nomenclature  it  must  be  mentioned  that 
my  plants  are  burdened  with  a  formidable  series  of  synonyms  from 
the  very  moment  that  they  appear.  Some  authors  regard  O.  La- 
marckiana as  a  variety  of  O.  biennis.  Others  separate  the  subgenus 
Onagra  as  a  distinct  genus.  O.  gigas  has  therefore  ihe  following 
equally  legitimate  synonyms  ;  • 

O.  gigas. 

Oenothera  Lamarckiana  gigas. 

Oenothera  biennis  gigas. 

Oenothera  biennis  Lamarckiana  gigas. 

Onagra  gigas. 

Onagra  Lamarckiana  gigas. 

Onagra  biennis  gigas. 

Onagra  biennis  Lamarckiana  gigas. 

The  same  is  true  of  the  other  new  forms.  It  may  also  be  noted  that 
Oenothera  is  written  by  many  authors  Onothera,  whilst  Lamarckiana 
mav  be  written  lamarckiana  or  Lamarkiana. 


The  Mutations  in  the  Lajnarckiana-Fauiily.       227 

as  that  of  0.  Lamarckiana.  It  is  much  more  densely 
clothed  with  foliage  than  the  parent  form,  a  state  of 
affairs  brought  about  by  the  fact  that  the  nodes  are 
closer  together  and  that  the  leaves  hang  down. 

The  inflorescences  are  extraordinarily  luxuriant,  with 
short  internodes,  broad  bracts  and  very  large  flowers 
which  form  a  much  fuller  and  more  beautiful  group  than 
those  of  0.  Lamarckiana.  The  fruits  are  short  and  thick 
and  more  or  less  conical ;  the  seeds  are  very  large. 

In  spite  of  the  high  degree  of  variability  which  this 
plant  exhibits  it  can  be  distinguished  with  ease  from  its 
relatives  at  every  stage  of  its  development.-^ 

This  species  arose  only  once  in  the  Lamar ckiana-isiru- 
ily  as  the  table  on  page  224  shows.  In  the  other  families 
it  has  also  only  appeared  twice. 

Its  appearance  was  on  this  wise.  In  1895  I  had  a 
crop  of  about  14,000  plants  constituting  the  4th  genera- 
tion of  the  Lamarckiana-ia.m{\y.  All  the  mutated  indi- 
viduals had  been  transplanted  from  this  crop,  and  the 
majority  of  the  Lamarckianas  had  been  weeded  out,  to 
give  more  space  to  those  which  were  to  provide  seed  for 
the  next  generation.  At  the  beginning  of  August  I  had 
about  1000  of  these  plants  in  flower,  but  many  were  still 
in  the  rosette  stage.  I  chose  32  of  the  strongest  and 
finest  of  these  rosettes  and  planted  them  in  a  separate 
bed  the  proper  distance  apart. 

These  plants  grew  up  the  next  year  and  flowered  in 
July  and  August.  One  of  them  caught  my  eye  with  its 
thick  stem,  rather  compressed  inflorescence  and  notice- 
ably larger  flowers.  On  the  10th  of  August  I  picked  off 
all  the  flowers,  both  the  open  ones  and  those  which  were 

^  For  a  more  detailed  description  of  this  and  the  other  new  spe- 
cies see  the  next  chapter. 


228  The  Pedigree  f  am  Hies. 

through  blooming,  enclosed  the  inflorescence  in  a  paper 
bag;  and,  later,  fertilized  the  flowers  myself  with  their 
own  pollen.  The  plant  set  a  quantity  of  seed ;  the  fruits 
were  short  and  thick,  the  seeds  large. 

This  plant  was  the  parent  of  the  new  species  O.  gigas. 
Its  ancestors  were  at  least  for  three  generations  ordinary 
O.  Lamarckiaiia.  The  new  form  arose  without  any  inter- 
mediate stages  or  previous  warning;  it  is  so  striking 
when  in  flower  that  it  could  not  have  been  overlooked  if 
it  had  existed  before.  And  it  must  be  remembered  that 
the  number  of  seed-bearing  plants  in  each  of  the  three 
generations  were  respectively  only  9,  6  and  10,  and  that 
they  were  under  continual  and  close  observation. 

The  self-fertilized  seeds  of  the  original  plant  of  O. 
gigas  were  sown  separately  in  1897.  They  gave  rise  to 
somewhat  over  450  plants.  All  of  them  proved  to  be 
like  their  parent  and  constituted  without  any  question  a 
type  distinct,  from  the  very  outset,  from  O.  Lamarckiana. 
Only  one  plant  did  not  conform  to  this  type;  it  had  all 
the  characters  of  O.  gigas,  but  possessed  the  dwarf  habit 
of  0.  nanella.  It  will  henceforth  be  referred  to  as  O. 
gigas  nanella.  Not  a  single  one  of  the  450  plants  re- 
verted to  O.  Lamarckiana. 

Lack  of  space  prevented  me  from  keeping  more  than 
a  quarter  of  this  crop  till  the  end  of  the  summer.  Many 
stayed  in  the  rosette  stage,  others  produced  stems  and 
flowered;  all  were  pure  O.  gigas.  I  saved  seed  from 
some  of  these  plants  whose  flowers  had  been  covered 
with  paper  bags  and  self-fertilized. 

This  experiment  proves  that  this  species  was  perfectlv 
constant  from  its  very  first  appearance.  And  it  remained 
so  for  the  three  subsequent  generations.^ 

^  And  afterwards,  until  now   (Note  of  1908). 


The  Mutations  in  the  Lamarckiana-F amity.      229 

We  may  postpone  further  details  of  this  case  to  a  later 
section  and  proceed  to  the  following  generalization  as 
being  fully  warranted  by  the  evidence. 

A  new  elementary  species  can  appear  without  any  oh- 
z'ious  cause  in  a  single  individual  and  he  absolutely  con- 
stant from  the  very  outset. 

As  I  have  already  stated  this  form  has  appeared  twice 
again  in  my  experiments. 

11.  O.  olbida.  A  pale  green,  rather  brittle,  and  very 
delicate  form  with  narrow  leaves;  never  attaining  any- 
thing like  the  height  of  0.  Lamarckiana  and  bearing 
pale  flowers  and  weak  fruits  which  contain  little  seed. 

It  appears  every  year  in  most  of  the  cultures  in  larger 
or  smaller  numbers ;  as  a  young  rosette  it  is  immediately 
recognizable.  They  are  so  weak  that  in  the  first  gen- 
erations I  imagined  them  to  be  diseased  and  did  not 
record  them ;  that  is  the  reason  for  the  absence  of  any 
mention  of  their  occurrence  in  the  years  1888  and  1890 
in  the  table  on  page  224. 

In  spite  of  their  frequent  appearance  it  was  not  till 
1896  that  I  could  get  one  of  them  to  flower.  I  mention 
this  in  order  to  allay  any  suspicion  that  crossing  may 
have  been  the  cause  of  their  repeated  appearance,  before 
the  6th  generation. 

All  that  remained  of  the  1895  crop  in  1896  was  a 
single  plant,  which  was  consequently  biennial.  A  few 
isolated  flowers  appeared  on  it  but  they  bore  scarcely 
any  pollen  and  set  no  seed  after  I  had  fertilized  them 
with  their  own  pollen  and  covered  them  with  a  paper 
bag. 

In  1897  however  I  succeeded  in  getting  five  biennial 
plants  to  flower;  and  in  obtaining  seed  from  them  after 
artificial    fertilization.      From    these    seeds    I    raised    a 


230  The  Pedigree  Families. 

second  generation  in  1898  and  a  third  in  1899,  both  of 
annual  individuals.  Both  generations  were  absolutely 
constant  and  exhibited  no  signs  of  reversion ;  but  con- 
sisted only  of  a  few  individuals  on  account  of  the  paucity 
of  the  harvest  which  each  generation  gave  (86  in  1898 
and  36  in  1899). 

III.  O.  rubrinervis.  A  beautiful  species  w^hicli  often 
has  red  veins  on  the  leaves  and  broad  red  stripes  on  the 
calyx  and  fruit.  Markings  of  this  kind  do,  it  is  true, 
occur  sometimes  on  0.  Lamar ckiana,  but  they  are  never 
so  pronounced  that  tlieir  possessors  could  possibly  be 
mistaken  for  O  ruhrinervis.  The  flowers  are  somewhat 
larger  and  a  rather  darker  yellow.  The  stem,  especially 
in  annual  cultures,  is  generall}^  shorter  than  that  of  La- 
marckiana  and  suffused  with  red.  The  species  cannot 
as  a  rule  be  recognized  in  the  very  young  rosette  stage '} 
in  fact  not  till  the  plant  has  10-20  leaves,  or  later  if  the 
plants  are  grown  too  close  together.  Ruhrinervis  was 
therefore  not  detected  until  after  the  latas  and  nanellas 
had  been  identified  and  removed.  It  is  then  easily  rec- 
ognizable by  its  narrow  and  long  leaves  with  red  veins, 
and  by  its  vigorous  habit. 

A  very  peculiar  feature  of  this  species  is  the  brittle- 
ness  which  characterizes  the  annual  forms  to  a  much 
greater  extent  than  the  biennial  ones.  The  stem  and 
leaves  can  be  broken  by  a  moderately  hard  blow.  If  such 
a  blow  is  administered  to  the  flowering  plant  from  above, 
the  stem  splits  into  several  pieces  with  perfectly  smooth 
surfaces  of  fracture.  The  cause  of  this  is  the  extra- 
ordinarily slight  development  of  the  bast-fibres  which 
however  are  not  entirely  lacking  as  microscopical  investi- 

'  The  distinguishing  characters  have  since  been  found  in  verv 
young  seedlings  (Note  of  1908). 


The  Mutations  in  the  Lamarckiana-F amily .       231 

gation  sliows.  If  a  fruit  is  pulled  off  without  great  care 
the  stem  is  usually  broken  in  the  process,  an  event  which 
has  more  than  once  caused  me  considerable  annoyance  at 
harvest  time. 

In  all  its  other  characters  O.  rubrinervis  is  a  very 
healthy  plant — quite  as  strong  as  O.  Lamarckiana  at  any 
rate.  It  is  the  only  one  of  my  new  species  which  is  not 
inferior  to  the  parent  type  in  richness  in  pollen  and  seed. 
Apart  from  its  brittleness  it  seems  to  be  fully  qualified 
for  the  struggle  for  existence.  I  have  not  however  yet 
organized  any  experiments  to  determine  this  point. 

0.  rubrinervis  appeared  in  the  main  line  of  descent, 
as  the  table  on  page  224  shows,  in  the  third,  fourth, 
fifth  and  sixth  generations.  There  were  32  examples 
of  it  altogether.  In  the  other  families  it  was  also  ob- 
served from  time  to  time;  and  appeared  as  early  as  1889 
in  the  laez'ifolia-immly.  In  1897  only  three  appeared  in 
the  main  line  of  the  Lamarckiana-i2im\\y,  whilst  10  ap- 
peared in  the  branch  lines  of  descent.  Their  ancestors 
for  at  least  five  generations  back  were  all  0.  Lamarckiana, 
or  at  least  not  of  the  rubrinervis  type. 

O.  rubrinervis  appears  each  time  without  visible  prep- 
aration :  and  what  strikes  one  most  is  the  absolute  con- 
stancy of  the  characters  although  these  were  quite  distinct 
from  those  of  its  ancestors. 

When  once  I  recognized  a  plant  in  its  rosette  stage 
as  being  a  rttbrinervis  I  could  predict  that  it  would  have 
a  fragile  and  brittle  stem  and  red  calyx  and  fruit.  This 
constancy  in  character  is  a  feature  of  all  my  new  ele- 
mentary species  and  is  even  more  striking  in  the  case  of 
O.  lata  than  in  rubrinervis. 

I  first  started  experiments  on  the  constancy  of  the 
new  rubrinervis  in  1896  and  1897.     In  1895  I  covered 


22^2 


The  Pedigree  Families. 


the  eight  individuals  which  appeared  in  that  year  and 
fertihzed  them  with  their  own  pollen,  (see  tahle  on  page 
224).  From  the  seeds  thus  obtained  I  raised  a  consider- 
able number  of  plants 
in  1896;  the  seeds  were 
sown  in  pans  and  all 
the  seedlings  picked  out 
onto  a  bed.  W^ith  the 
exception  of  a  few  that 
were  to  serve  as  seed- 
parents,  they  were  all 
pulled  up  while  they 
were  flowering  ( from 
August  to  October)  i. 
e.,  not  before  the  time 
when  the  rubrinerms- 
character  was  fully  de- 
veloped in  the  stalk, 
calyx,  flower  and  young 
fruit.  There  were  some 
young  stems  and  ro- 
settes left  over  after 
this  process,  but  these 
also  proved  to  be  ex- 
amples of  riihrinervis. 
The  number  of  plants 
that  flowered  amounted 
to  about  1000.  Among 
these  was  a  single  La- 


Fig.  43.  Oenothera  riihrinervis.  Top 
of  the  plant,  showing  flowers,  buds, 
and  unripe  fruits. 


iiiarckiana  which  had 
presumably  grown  from  a  seed  left  in  the  bed  from  last 
year's  sowing.  Otherwise  all  the  plants  were  rubri- 
nervis;   except   that    some   of   them    also   exhibited   the 


The  Mutations  in  the  Lamarckiana-Fajnily.       233 


features  of  Oenothera  leptocarpa,  a  new  species  at  that 
time. 

The  existence  of  the  single  Laiuarckiana  was  i)lainly 
a   difficulty,    so   that   I 
not  only  continued  but 
repeated     the     experi- 
ment. 

For  the  continua- 
tion of  the  experiment 
I  used  the  seeds  saved 
in  1896.  I  raised  from 
them,  in  1897,  1114 
plants;  every  single  one 
of  which  was  a  riibri- 
nervis. 

For  the  repetition 
of  the  experiment  I 
used  the  self-fertilized 
seeds  of  the  four  plants 
which  had  arisen  in 
1896  from  the  Laniarc- 
kiana-i^mily  and  could 
therefore  boast  four 
generations  of  pure 
Lamar ckiana  ancestry. 
From  these  seeds  I 
raised  altogether  1862 
plants,  which  were 
without  exception  riib- 
'  rinerz'is. 

From  these  facts  I  conclude : 

1.   That  rnbrinervis  is  an  absolutely  ci^nstant  elemen- 
tary species. 


Fig.  44.  Oenothera  ohlonga.  Upper 
part  of  a  plant  at  the  commence- 
ment of  flowering. 


234  The  Pedigree  Families. 

2.  That  every  example  of  nihrinervis  that  arises  in 
a  family  of  another  kind  is  capable  of  producing  per- 
fectly constant  progeny. 

IV.  0.  ohlonga.  The  seedlings  of  this  species  can 
first  be  recognized  as  such  at  the  appearance  of  about  the 
sixth  leaf,  that  is  a  little  after  0.  lata  and  O.  nanella  and 
consideral)ly  earlier  than  0.  rubrinervis  and  0.  scintil- 
laiis.  The  leaves  are  narrow  and  with  long  stalks ;  the 
transition  from  the  leaf  to  its  stalk  is  not  gradual  but 
abrupt,  and  the  broad  and  pale  veins  have  a  reddish 
tinge  underneath.  0.  ohlonga  can  only  be  recognized 
uniformly  early  when  the  plants  among  which  it  appears 
are  grown  sufficiently  far  apart,  but  if  the  undoubted 
examples  of  ohlonga  are  removed  from  time  to  time  more 
examples  of  it  will  be  found  as  a  result  of  the  additional 
space  put  at  the  disposal  of  the  plants. 

The  typical  form  of  the  leaf,  to  which  we  have  re- 
ferred, was  maintained  in  the  rosettes  that  were  planted 
out.  Some  of  the  plants  bore  stems  in  the  first  year, 
others  turned  out  to  be  biennials.  In  both  cases  the  plants 
reach  a  moderate  height  only,  rarely  attaining  a  meter 
in  height  and  being  very  much  smaller  than  plants  of 
Lamarckiana  grown  under  identical  conditions.  The 
annual  forms  branch  but  little,  and  the  branches  them- 
selves remain  short.  The  terminal  spikes  are  thickly 
covered  with  flowers  and  buds ;  the  flowers  themselves 
are  smaller  than  in  0.  Lamarckiana  and  develop  small 
fruits  which  contain  verv  little  seed.  The  biennial  forms 
branch  more,  and  bear  plenty  of  pollen ;  they  form  short 
1)ut  stout  fruits  which  contain  abundance  of  seed. 

Towards  the  end  of  their  flowering  period  the  oh- 
longa plants  can  be  recognized  from  quite  far  off  by  the 


The  Mutations  in  the  Laniarctziana-Fcunily.       235 

way  in  which  their  small  unripe  fruits  are  crcjwded  to- 
gether. 

In  tlie  fourth  generation  of  my  Lamarckiana-i2i\w\\\ 
(grown  in  1895  and  consisting  of  14,000  plants)  there 
were  176  O.  oblonga;  in  the  fifth  generation  (grown  in 
1896  and  consisting  of  8000)  there  were  135.  That  is, 
in  the  one  case  1.3,  in  the  other  1.7  %.  In  the  sixth  gen- 
eration this  proportion  was  maintained  (29  in  1800  = 
1.6%).  In  the  last  two  the  number  has  been  mucli 
smaller  because  the  counting  had  to  be  discontinued  too 
early. 

In  1896  I  got  seeds  from  biennial  plants  of  the  fourth 
generation,  and  from  annual  ones  of  the  fifth  by  arti- 
ficial self-fertilization  in  paper-bags.  There  were  seven 
of  the  biennial  seed-parents :  each  of  them  produced  be- 
tween two  and  three  hundred  seeds  wdiich  were  sown 
in  separate  lots.  Altogether  1683  plants  were  raised  from 
them.  They  were  all  oblonga  with  the  exception  of  one 
which  had  the  characters  of  albida.  There  were  no  ex- 
amples of  Lamarckiana  among  them. 

Ten  of  the  annual  plants  of  the  fifth  generation  set 
seed  which  was,  however,  scanty  and  germinated  badl}-. 
Only  64  plants  were  raised ;  of  these  one  was  O.  nibri- 
nervis,  the  rest  oblonga.     There  were  no  Laniarckianas. 

I  have  tested  the  constancy  of  other  examples  oi  ob- 
longa wdiich  have  arisen  in  other  families  with  the  same 
result. 

Oenothera  oblonga  is,  therefore,  perfectly  constant 
directly  it  arises,  but  it  has  the  power  of,  itself,  giving 
rise  to  new  forms. 

V.  0.  nanclla  (O.  Lamarckiana  nanclla).  Dwarf 
Oenothera.  We  are  not  now  concerned  with  the  ques- 
tion whether  a  particular  form  is  to  be  described  as  a  spe- 


236 


The  Pedigree  Families. 


\ 


cies  or  as  a  variety.  Our  business  is  to  test  its  constanc}- 
by  experiment.  But  tbe  result  of  this  will  not  help  us 
to  decide  between  species  and  variety. 


^^j^gfy*  ^v>»^ 


Fig.  45.  Oenothera  nanella.  A  thinly  and  a  densely  leaved 
individual  on  one  of  the  first  days  of  the  flowering  pe- 
riod. The  plants  were  about  15  and  20  cm.  high,  whereas 
annual  plants  of  O.  Lamar ckiana  begin  to  flower  when 
they  are  about  one  meter  high. 

If  a  form  proves  to  be  constant  but  is  distinguished 
from  another  form  onlv  bv  a  single  character,  it  is  re- 


\ 


i 


The  Mutatiofis  in  the  Lamarckiana-Family.      237 

garded  by  most  authorities  as  a  variety;  and  this  is  es- 
pecially the  case  with  dwarf  forms,  which  are  known  for 
a  whole  series  of  species,  and  attain  only  half  or  less  of 
the  stature  of  the  species  to  which  they  belong. 

On  this  ground  O.  nanella  may  be  regarded  as  a 
variety;  but  it  must  not  be  forgotten  that,  from  the 
experimental  point  of  view,  it  is  just  as  good  an  element- 
aiy  species  as  those  which  we  have  described  already.^ 

The  dwarfs  are,  perhaps  with  the  exception  of  0. 
lata,  the  easiest  to  recognize  in  my  cultures.  They  ap- 
peared annually,  in  every  culture,  except  the  smaller  ones. 
Among  the  50,000  individuals  which  composed  the  whole 
Lamar ckiana-idirmXy ,  1 58  were  nanella ;  that  is  about 
0.3%,  a  proportion  which  was  remarkably  constant  in 
successive  years. 

The  dwarfs  can  be  easily  and  certainly  recognized 
during  the  whole  course  of  their  development.  If  grown 
far  apart  and  well  lighted  they  are  recognizable  as  soon 
as  the  second  leaf  appears;  the  first  leaf  is,  at  that  time, 
broad  with  a  broad  almost  heart-shaped  base  closely  set 
on  its  short  petiole.  In  1897  I  identified  and  recorded 
them  by  this  character.  Plants  about  which  there  was 
the  slightest  doubt  were  allowed  to  develop  further. 

The  broad  stumpy  leaves  are  succeeded  by  one  or 
two  lozenge-shaped  ones  with  long  stalks ;  and  the  plant 
looks  as  if  it  were  reverting  to  O.  Lamarckiaiia.  This 
however  is  not  the  case,  for  there  soon  follow  a  number 
of  very  broad  leaves,  with  very  short  petioles,  closely 
crowded  together;  with  the  result  that  the  highly  char- 
acteristic dwarf  rosette  is  formed.  The  way  I  dealt 
with  these  plants  in  1896  was  to  plant  them  out  after 

^Jordan,  {De  Torigine  dcs  orhrcs  fruitiers,  1853)  has  pointed 
out  that  varieties  are  only  a  special  form  of  elementary  species. 


238  The  Pedigree  Families. 

the  second  leaf  had  appeared  in  well  manured  soil  and  at 
a  good  distance  apart.  They  were  about  6  weeks  old 
when   I   finally   identified  them. 

The  rosettes  nearly  always  bore  a  stem  in  the  first 
year;  I  only  obtained  biennial  plants  by  sowing  the  seed 
late  or  by  crowding.  The  biennial  form  is  richly  branched  ; 
the  annual  has  very  few  lateral  branches  (Fig.  45).  The 
internodes  are  numerous  and  very  short,  the  broad  short- 
stalked  leaves  are  therefore  much  crowded.^  The  petioles 
are  brittle.  The  first  flowers  often  open  when  the  plant 
has  scarcely  reached  a  height  of  10  centimeters;  after 
their  first  appearance  flowers  are  usually  born  at  regular 
intervals  but  sometimes  sporadically.  The  flowers  are 
almost  as  big  as  those  of  O.  Lamarckiana ;  so  that  the 
plant  in  flower  is  very  showy.  The  fruits  are  not  per- 
ceptibly smaller  than  those  of  the  parent  species. 

In  order  to  protect  the  first  flowers  from  the  visits 
of  insects  I  enclosed  the  whole  plant  in  a  bag  of  parch- 
ment, the  margin  of  which  is  attached  to  a  metal  ring 
which  is  firmly  pressed  into  the  ground.  It  is  not  until 
the  inflorescences  have  attained  a  considerable  length 
that  the  flowers  can  be  enclosed  in  parchment  bags  in  the 
ordinary  way. 

The  first  dwarfs  I  fertilized  in  this  way  were  some 
which  flowered  in  1893.  Their  ancestors  which  had  not 
been  protected  from  the  visits  of  insects  and  only  in- 
completely isolated  had  notwithstanding  this,  already  ex- 
hibited a  high  degree  of  constancy.  The  seeds  collected 
in  1893  gave  rise  to  440  seedlings  which  were  all  nanella. 

In  1895  I  self-fertilized  a  series  of  dwarfs  which 
arose  in  the  fourth  generation  of  my  Lamar ckiana-ia.m'i\y 

^  The  characteristics  of  the  dwarfs  are  in  part  due  to  a  disease; 
see  §  i8  (Note  of  1908). 


The  Mutations  in  the  Lamarckiana-family.       239 

and  had  therefore  at  least  three  generations  of  ancestors 
with  the  normal  high  stature.  In  the  same  year  I  also 
sowed  some  seed  saved  from  the  second  generation  (1888- 
1889)  and  I  self-fertilized  some  of  the  dwarfs  that  ap- 
peared in  the  crop  thus  raised.  There  were  altogether 
20  of  them ;  they  set  a  quantity  of  seed  from  which  2463 
seedlings  were  grown.  They  were  without  exception 
0.  nanclla. 

Thus  we  see  that  every  one  of  the  twenty  dwarfs  which 
arose  spontaneously  from  O.  Lauiarckiana  had  a  perfectly 
constant  progeny.  As  I  have  already  stated,  the  plants 
were  not  registered  as  dwarfs  until  they  were  strong 
rosettes  and  had  attained  the  age  of  about  six  weeks. 

I  repeated  the  experiment  on  a  larger  scale  in  the 
following  year,  when  I  had  found  out  how  to  identify 
the  plants  without  transplanting  them.  I  used  the  seeds 
of  nanella  plants  which  had  arisen  in  the  fifth  generation 
of  the  Lamarckiana-isimWy,  i.  e.,  plants  whose  ancestors 
had  therefore  been  normal  for  four  generations.  From 
the  seeds  of  36  plants  I  raised  over  18,000  seedlings. 
These  were  without  exception  nanella ;  but  3  of  them  ex- 
hibited in  addition  to  the  dwarf  habit  the  characters  of 
O.  ohlonga  and  constituted  an  elementary  species  of  the 
second  grade,  O.  nanella  ohlonga. 

Moreover,  whenever  nanella  appeared  in  other  fam- 
ilies it  proved  immediately  constant,  not  only  in  the  first 
but  in  succeeding  generations  as  well. 

Combinations  with  other  characters  occurred  in  these 
cultures ;  but  very  rarely.  I  have  often  had  examples 
of  0.  lota  nanella  and  O.  nanella  elliptica,  and  now  and 
again  variegated  or  pitcher  forming  individuals  of  0. 
nanella,  and  so  on. 

VI.    O.  lata.     This  species  is  solely  female:    it  never 


240  The  Pedigree  Families. 

forms  the  slightest  trace  of  pollen.^  With  the  pollen  of 
i^amarckiana  or  any  of  its  deviations  it  is  perfectly  fertile 
and  gives  a  proportion  of  /a/a-plants  which  varies  about 
15-20%. 

Julius  Pohl  has  investigated  the  cause  of  its  steril- 
ity.^ The  pollen  sacks  of  the  open  flower  are  dry  to  the 
touch ;  they  seem  to  be  empty,  but  as  a  matter  of  fact 
contain  a  little  pollen  which  is  seen  under  the  microscope 
to  consist  of  empty  grains  which  are  not  merely  poor  in 
protoplasm  but  shrivelled  and  stunted.  The  development 
of  the  anthers  is  at  first  normal,  up  to  the  formation  of 
tetrads.  About  this  time  the  surrounding  cells  of  the 
tapetum  elongate ;  and  subsequently  grow  into  the  cav- 
ity of  the  sack.  These  cells  disappear  at  a  later  stage, 
when  the  pollen  grains  may  be  found  lying  in  the  mucus 
which  they  leave  behind. 

I  spent  a  great  deal  of  time  in  transferring  these 
scanty  masses  of  pollen  to  the  stigma  in  the  hope  of 
obtaining  a  few  seeds  if  possible,  but  all  in  vain.  If 
the  visits  of  insects  were  prevented  the  plants  set  no  seed. 

The  exclusively  female  character  of  this  mutant  is 
very  important,  for  it  shows  in  a  most  direct  way  that 
the  remarkably  regular  production  of  O.  lata  year  after 
year  in  the  Lamarckiana-i3.m\\y  cannot  be  due  to  acci- 
dental crossing — an  explanation  of  the  frequency  and 
regularit}^  of  its  appearance  which  is  also  disproved  by 

'  Of  late  I  have  discovered  a  hybrid  strain  of  lata  which  produces 
pollen  in  a  greater  or  smaller  part  of  its  flowers.  These  plants,  when 
self-fertilized,  produce  seed,  which  gives  15-20  %  examples  of  lata] 
and  80-85  ^c  of  Lamarckiana.  Also  the  same  figures  as  by  pollina- 
tion with  the  parent-species.  This  proves  the  O.  lata  to  be  an  in- 
constant species.  Seeds  of  this  strain  have  been  distributed  to  some 
of  my  correspondents,  who  also  found  the  type  to  be  inconstant. — 
(Note  of  1908.) 

"Julius  Pohl,  Ucher  Varintionszvcite  dcr  Oenothera  Lamarc- 
kiana, Oesterr.  bot.  Zeitschrift,  1895,  Nos.  5-6. 


The  Mutations  in  the  Larnarckiana-Family.       241 

the  artificial   fertilization  of  the  whole  ancestry  in  my 
pedigree-cultures. 


Fig.  46.  Oenothera  lata.  Top  of  a  stem,  with  buds  in  the 
axils  of  the  broad  bracts  ;  a,  b,  c,  separate  buds  in  various 
stages  of  development;  A,  B,  C,  buds  of  Oenothera  La- 
marckiana  in  corresponding  stages.  The  buds  of  lata  are 
seen  to  be  palpably  fatter  than  those  of  O.  Laniarckiana. 


0.  lata  can  easily  be  distinguished  at  every  stage  of 
its  existence  from  all  its  allies ;  in   fact  as  soon  as  the 


242  The  Pedigree  Families. 

second  or  third  leaf  unfolds:  these  leaves  are  broad  with 
broad  bases  and  long  petioles.  But  most  characteristic 
is  the  broad  and  round  shape  of  the  tip  of  the  leaf,  a  fea- 
ture which  is  more  or  less  distinctly  pronounced  during 
all  the  rest  of  the  life  of  the  plant.  The  plants  are  always 
low  although  the  rosettes  are  large  and  strong,  stronger 
sometimes  than  those  of  Lamarckiana  itself.  The  stem 
is  limp  so  that  the  top  hangs  over  to  the  side  even  in  the 
healthiest  plants.  It  is  thickly  covered  with  dense  foliage. 
The  leaves  are  rounded  at  the  apex  and  much  crumpled. 
The  top  of  the  growing  stem,  both  in  its  young  stages  and 
when  it  is  covered  with  flowers,  is  in  the  form  of  a  com- 
pressed rosette. 

Everything  in  this  plant  is  stout  and  broad,  so  that 
they  came  to  be  known  among  us  in  the  garden  as  ''fat- 
heads." This  character  w^as  particularly  noticeable  in 
the  case  of  the  flower-buds  just  before  they  opened,  and 
has  been  well  brought  out  by  Pohl^s  figures.  The  petals 
do  not  unfold  themselves  completely  but  remain  more 
or  less  wrinkled.  The  stigmas  are  peculiar.  As  in  the 
case  of  O.  Lamarckiana  their  number  varies  from  a  nor- 
mal of  four  up  to  8  and  more,  forming  a  so-called  half- 
curve.  This  matter  has  been  made  the  subject  of  a  thor- 
ough study  by  Verschaffelt  in  the  case  of  0.  La- 
marckiana. The  fusion  of  neighboring  stigmas,  which 
occurs  in  the  parent  form,  occurs  in  O.  lata  also.  The 
unequal  development  of  the  stigmas  which  occurs  now 
and  again  in  Lamarckiana  is  exaggerated  to  an  extra- 
ordinary extent  in  the  daughter  species;  and  the  most 
curious  malformations  arise  as  the  result  of  the  fusion 
referred  to.-^  They  do  not  however  interfere  with  fertili- 
zation. 

^  For  figures  of  these  see  Pohl's  paper,  loc.  cit.,  Taf.  X,  Fig.  27. 


The  Mutations  in  the  Larnarckiana-Fainih.       243 

The  fruits  are  short  and  thick  and  contain  relatively 
few  but,  as  a  rule,  large  seeds. 

O.  lata  appeared  pretty  regularly  in  my  cultures,  but 
in  proportions  which  varied  greatly.  And  as  they  could 
be  easily  and  certainly  recognized,  even  under  unfavor- 
able circumstances  such  as  crowding,  these  deviations 
are  indices  of  a  real  variability  in  proportions  and  not 
of  the  difficulty  of  identification  which  may  have  affected 
the  proportions  in  the  case  of  the  other  forms.  The  pro- 
portion of  lata  plants  was  sometimes  as  low  as  0.1%  ;  in 
the  fifth  generation  it  was  as  high  as  1.8%  ;  i.  e.,  about 
the  same  as  that  of  O.  oblong  a. 

VII.  O.  scintillans.  Except  for  0.  gigas  which  has 
so  far  only  arisen  three  times,  and  0.  spathulata,  0.  subo- 
vata,  O.  leptocarpa  and  others  which  I  shall  refer  to  later 
on,  O.  scintillans  is  by  far  the  rarest  form  in  my  cultures. 
It  arose  only  eight  times  in  the  Lamarckiana-idimWy ,  and 
in  other  families  still  more  seldom. 

It  does  not,  like  the  other  species,  breed  true  when 
self-fertilized,  but  behaves  in  a  very  peculiar  way.  Seeds 
from  it  give  rise  to  three  forms  in  considerable  numbers : 
0.  scintillans,  O.  oblonga  (Fig.  44  on  page  233)  and  0. 
Lamarckiana. 

This  is  a  different  phenomenon  from  that  with  which 
we  are  already  familiar  in  the  other  elementary  species, 
namely  the  ver}^  occasional  production  of  a  mutation  in 
about  1  in  1000  plants.  There  often  arise  in  this  way 
elementary  species  of  the  second  order,  i.  e.,  species  which 
combine  the  characters  of  two  species.  These  also  arise 
in  the  case  of  0.  scintillans;  e.  g.,  0.  scintillans  nanclla 
and  0.  scintillans  elliptica.  But  only  very  occasionally, 
i.  e.,  one  such  among  thousands  of  normal  O.  scintillans. 

A  verv  remarkable  feature  of  this  instabilitv  of  O. 


244 


The  Pedigree  Families. 


scintillans  is  that  the  proportions,  in  which  the  different 
forms  occur,  are  by  no  means  low  at  first,  and  that  they 

cannot  be  increased  by  selec- 
tion. Perfectly  definite  prin- 
ciples underlie  these  propor- 
tions ;  for  the  behavior  of  an 
O.  scintillans  from  one  stock  is 
the  same  as  that  derived  from 
another. 

Some  mutants  of  O.  scin- 
tillans had  a  capacity  of  produ- 
cing 35-40  %  scintillans;  and 
others  a  capacity  of  producing 
70  %  or  more.  Moreover,  this 
capacity  seems  to  be  inherited. 
I  first  noticed  O.  scintillans 
in  1888,  in  a  culture  from  seeds 
of  the  /a/a-family  (§7).  The 
plant  was  biennial :  I  did  not 
sow  its  seeds  till  1894.  In  1895 
I  fertilized  some  of  them 
(which,  it  will  be  seen,  flow- 
ered in  their  second  year)  with 
their  own  pollen.  I  treated  14 
plants  in  this  way,  but  they  set 
little  seed.  In  1896 1  raised  only 
400  plants  from  them  as  fol- 
lows : 

68  %   O.  Lamarckiana 


Fig 


47.    Oenothera  scintil- 
lans. Top  of  an  annual  plant. 


15  %   O.  scintillans 
15  %    O.  oblong  a 
2  %   O.  lata 


and  one  plant  of  O.  nanella. 


The  Mutations  in  the  Lamarckiana-Family.      245 

In  1898  there  arose  in  another  0.  /a/a-family  a  single 
example  of  0.  scintillans  which  flowered  in  its  first  year 
and  was  self-fertilized  in  a  bag.  148  young  plants  were 
raised  from  its  seeds,  as  follows : 

55  %   O.  Lamarckiana 
Z7  %   0.  scintillans 
7  %   O.  oblong  a 
1  %   O.  lata. 
I  have  tested  the  hereditary  capacity  of  three  exam- 
ples of  0.  scintillans  which  arose  directly  from  the  0. 
Lamar ckiana-i2im\\y.     The  first  was  a  plant  which  arose 
in  1895  but  did  not  flower  till  1896;  it  had  a  number  of 
lateral  stems  on  all  of  which  the  flowers  were  fertilized. 
The  various  sowings  of  their  seeds  gave  the  following 
species  and  proportions : 

52-59  %   O.  Lamarckiana 
34-36  %   O.  scintillans 
3-10  %   0.  oblonga 
1  %   O.  lata. 
I  manas:ed  to  obtain  self-fertilized  seeds   from  nu- 
merous  O.  scintillans  which  appeared  in  this  culture ;  the 
proportions  of  the  various  kinds  produced  by  them  were 
subject  to  considerable  fluctuation,  but  they  were  essen- 
tially the  same  as  those  given  by  their  parents. 

Of  the  six  plants  which,  as  shown  in  the  table  on  page 
224,  arose  (1896)  in  the  fifth  generation  of  0.  La- 
marckiana I  only  succeeded  in  bringing  two  through  the 
winter  and  in  getting  them  to  flower  (1897).  They  were 
self-fertilized  in  bags.  The  seeds  of  one  plant  gave  like 
the  others : 

51  %   0.  Lamarckiana 
39  %   O.  scintillans 
8  %   O.  oblonga 


246  The  Pedigree  Families. 

1  %   0.  lata 

1  %   0.  nancUa. 

But  the  second  plant  gave  a  much  "better"  result  for 
the  200  seedlings  were  distributed  as  follows : 

8  %   0.  Lamarckiana 
69  %   O.  scintiUans 
21  %   O.  oZ^/on^ra 

2  %   0.  lata,  O.  nan  ell  a,  etc. 

I  fertilized  about  25  of  those  O.  scintiUans  with  their 
own  pollen.  I  sowed  the  seeds  of  each  one  separately 
and  got  a  proportion  of  scintiUans  in  the  next  generation 
varying  between  66  and  93  %  about  a  mean  of  84  %. 
One  plant  seemed  to  give  O.  scintiUans  only ;  but  the  crop 
from  this  plant  was  small.  In  1899  and  1900  I  continued 
my  experiments  in  the  same  way,  in  order  to  find  out 
whether  this  species  could  be  brought,  by  selection,  to  the 
same  level  of  constancy  as  that  which  characterizes  the 
other  elementary  species. 

Perhaps  some  day  there  will  appear  in  the  Lamarc- 
kiana-i2irm\y  or  in  some  other  a  scintiUans  which  will 
breed  true  straight  away. 

An  estimation  of  the  constancy  of  scintiUans  mutants 
has  been  made  four  times  in  all.  Three  times  it  gave 
offspring  like  itself  in  the  proportion  of  34-39  %  ;  in  the 
next  generation  it  did  the  same.  In  the  fourth  instance 
the  proportion  was  69  %  and  the  mean,  in  the  next  gen- 
eration, had  mounted  to  84  %.  These  numbers  show 
in  my  opinion  that  0.  scintiUans  is  an  inconstant  species 
which  moreover  tends  to  give  rise  on  its  first  appearance 
to  other  forms  and  especially  to  O.  ohlonga.^ 


*  The  deviation  in  the  first  series  of  figures  (15  %  instead  of  34- 
39%)    which   occurred   in   a   second   generation,   from    a   scintiUans 


The  Laws  of  Mutation.  247 

It  now  remains  to  give  a  short  description  of  the  spe- 
cific character  of  this  form. 

Scintillans  cannot  be  recognized  until  quite  late  :^  as 
a  rule  they  could  not  be  identified  before  the  rosettes  had 
quite  a  considerable  number  of  leaves  about  10  cm.  long. 
The  leaves  are  small,  narrow  and  with  long  petioles ; 
with  shiny  surface  (whence  the  name),  dark  green,  and 
with  hardly  any  trace  of  crumpling.  The  veins  are 
white  and  often  broad.  The  ends  of  the  leaves  turn 
down,  so  that  the  leaf  makes  an  arch  over  the  ground. 
The  stems  never  attain  a  great  size ;  they  are  thin  and 
l)ear  short  leaves;  they  produce  flowers  early,  forming- 
long  spikes.  The  annual  forms  are  usually  only  feebly 
branched ;  the  biennial  ones  more  profusely.  The  flow- 
ers are  small ;  a  little  smaller  or  about  the  same  size  as 
those  of  0.  biennis.  As  in  O.  Lamar ckiana,  the  stigmas 
project  beyond  the  anthers.  The  fruits  are  small,  the 
quantity  of  seed  in  annual  plants  is  also  small ;  and  many 
of  the  plants  begin  to  flower  too  late  to  set  any  seed 
at  all. 

The  dark  green  color  and  shiny  surface  occurs  on  tlic 
stem  leaves  as  well,  and  gives  the  plant  a  peculiar  a])- 
pearance  quite  different  from  that  of  0.  Lamarckiana. 

§  4.    THE  LAWS  OF  MUTATION. 

I  propose  now  to  recapitulate  the  conclusions  which 
I  have  drawn  from  my  experiments.  The  various  ele- 
mentary species  we  have  dealt  with  behave  in  essentially 
the  same  way;  so  also  does  a  secondary  branch  of  the 

whose  proportion  in  the  first  generation  is  unfortunately  unknown, 
seems  also  to  point  to  some  susceptibility  of  this  proportion  to  factors 
we  do  not  yet  understand. 

*  Since  writing  this,  I  haA^e  succeeded  in  recognizing  them  as 
young  seedlings,  with  only  2-4  leaves  (Note  of  1908). 


248  The  Pedigree  Families. 

family  we  have  just  considered,  as  well  as  two  other 
primary  families  which  will  be  described  in  section  5 ; 
not  to  mention  a  number  of  subsidiary  families  and  cul- 
tures. The  main  conclusion  is  that  the  facts  of  muta- 
bility can  be  described  by  laws  just  as  definite  as  the  laws 
of  variability. 

The  following  generalizations  apply  in  the  first  in- 
stance to  the  new  forms  which  have  arisen  from  Oeno- 
thera Lamarckiana;  but  it  should  be  stated  that  they  are 
completely  in  accordance  w^ith  a  whole  host  of  observa- 
tions, for  the  most  part  of  a  horticultural  nature,  on 
other  genera  and  families. 

I.  N'ezu  elementary  species  arise  suddenly,  without 
transitional  forms.  A  great  point  in  my  experiments 
has  been  that  the  ancestors  of  the  newly  arisen  forms 
have  always  been  accurately  known,  and  often  for  many 
generations  back;  and  that  they  were  either  isolated  as 
a  group  (1887-1891)  or  that  they  flowered  in  isolating- 
bags  and  were  artificially  fertilized  (1894-1899).  There 
is  no  mention  of  any  such  precaution  in  horticultural 
records.  This  precaution  enables  us  to  be  certain  that 
each  new  form  arose  from  the  seed  of  a  normal  specimen 
of  Oenothera  Lamarckiana.  The  new  form  always  arises 
with  all  the  characters  proper  to  it.  Once  the  identity 
of  a  seedling  is  recognized  the  characters  which  it  will 
gradually  assume  can  be  predicted,  and  in  every  case  the 
prediction  has  been  fulfilled. 

Many  opportunities  for  testing  the  degree  of  cer- 
tainty in  identifying  seedlings  offered  themselves  during 
the  course  of  the  experiments,  and  especially  when  the 
chosen  seedlings  were  planted  out  and  flowered  in  my 
garden. 

When  there  are  hundreds  of  individuals  to  record, 


The  Laws  of  Mutation.  249 

it  Is  natural  that  one  should  occasionally  be  in  doubt 
over  some  of  them ;  particularly  over  such  as  happen  to 
grow  between  others,  and  have  not,  on  that  account, 
sufficient  space  for  their  full  development.  I  have  usually 
given  these  plants  an  additional  lease  of  life,  in  many 
cases  the  whole  summer.  They  then  very  soon  proved 
to  be  a  pure  type ;  or  perhaps,  to  be  compound  forms 
such  as  0.  lata  nanclla,  O.  scintillans  elliptica  and  so 
forth,  or,  lastly,  new  forms  altogether.  But  they  never 
turned  out  to  be  intermediate  forms.  Transitions  be- 
tween the  various  elementary  species  did  not  occur. 

As  a  matter  of  fact  I  have  thought  on  one  or  two 
occasions  that  I  had  discovered  examples  of  such  inter- 
mediates. For  example  \  once  noticed  a  plant  which  was 
like  O.  lata  in  many  respects  but  bore  plenty  of  pollen. 
I  fertilized  the  plant  artificially  and  raised  270  plants 
from  its  seed.  These  were  all  like  their  parent  except 
for  1  %  of  them  which  were  true  lata,  that  is  to  say  no 
larger  a  percentage  of  O.  lata  than  the  Laniarckiana- 
family  Itself  can  give  rise  to.  I  have  called  this  form 
O.  semilata  (§  17).  Other  cases  of  a  similar  nature  have 
been  observed. 

The  seed  of  a  newly  arisen  form  will,  If  sown,  always 
give  rise  to  plants  with  exactly  the  same  characters  as 
their  parents :  and  this  purity  of  the  new  form  is  main- 
tained in  subsequent  generations. 

II.  New  elementary  species  are,  as  a  rule,  absolutely 
constant  from  the  moment  that  they  arise.  The  seeds 
set  by  an  example  of  a  newly  arisen  species  after  arti- 
ficial self-fertilization  give  rise  solely  to  plants  like  itself; 
without,  as  a  rule,  any  trace  of  reversion  to  its  parental 
form. 

This  is  equally  true  of  O.  gigas  which  has  only  arisen 


2dO  The  Pedigree  Faniilies. 

three  times,  and  of  forms  which  have  appeared  as  fre- 
quently as  have  0.  albida,  0.  ohlonga,  O.  rubrinervis  and 
O.  nan  el  I  a. 

The  point  cannot  be  decided  in  tlie  case  of  O.  laevi- 
folia  or  O.  brevistylis,  both  of  which  were  found  on  the 
spot  where  O.  Lamarckiana  was  originahy  discovered, 
but  have  not  arisen  in  my  cuhures.  Both  these,  when 
self-fertihzed,  come  perfectly  true  from  seed.  O.  hrevi- 
stylis  breeds  true  in  spite  of  its  small  fruits  which  some- 
times set  no  more  than  a  solitary  seed.  Indeed  I  thought 
at  first  that  these  fruits  were  absolutely  sterile. 

Oenothera  scintillans  and  0.  lata  are  exceptions  to 
this  rule.  The  seeds  borne  by  self-fertilized  plants  of 
the  first  named  form  produce  a  generation  only  about 
one-third  of  which  is  0.  scintillans.  This  is  true  of  the 
seeds  of  three  distinct  individuals  which  have  arisen 
quite  independently  of  one  another.  From  the  seed  of 
a  fourth  individual  however  69  %  of  O.  scintillans  were 
raised ;  and  these  again  in  the  next  generation  gave  from 
60  to  90  %.i 

This  constancy  of  the  new  species  is  an  extremely 
important  characteristic.  It  has  enabled  O.  laez'i folia 
and  0.  brez'istylis  to  maintain  themselves  in  the  spot 
where  they  arose — mere  scattered  examples  among  the 
host  of  Laniarckianas  which  surround  them ;  and,  what 
is  more,  pure  in  respect  of  all  their  characters  (apart  of 
course  from  accidental  crossing) 

That  the  struggle  for  existence  is  a  pretty  keen  one 
in  the  field  in  question  may  be  gathered  from  the  fact 
that  a  vigorous  Lamarckiana  can  bear  1 00  fruits  and  that 
each  fruit  contains  between  200  and  300  seeds.  The  whole 

^  For  further  information  on  this  point  see  section  19  of  this 
part. 


The  Laws  of  Mutatioii.  251 

field  contains  no  more  than  some  thousands  of  plants, 
that  is  to  say  not  much  more  than  could  be  supplied  by 
the  seeds  of  a  single  individual.  The  seeds  which  do 
not  produce  adult  plants  either  do  not  germinate  or  the 
seedlings  which  come  up  die  young.  Yet  in  spite  of  the 
severity  of  the  competition,  O.  laevifolia  and  O.  hrcvi- 
stylis  have  maintained  themselves  for  more  than  twelve 
years. -^ 

III.  Most  of  the  new  forms  that  have  appeared  are 
elementary  species,  and  not  varieties  in  the  strict  sense 
of  the  term.  Elementary  species  are  distinguished  from 
their  nearest  allies  by  nearly  if  not  quite  all  their  char- 
acters. The  differences  are  often  so  slight  as  to  escape 
notice  by  an  eye  not  trained  to  observe  them ;  and  they 
are  particularly  apt,  as  systematists  so  often  complain, 
to  become  lost  in  dried  specimens.  This  latter  is  how- 
ever fortunately  not  the  case  with  the  new  forms  whose 
origin  I  have  witnessed ;  for  they  are  distinguishable 
from  one  another  and  from  O.  Lamarckiana  as  herbarium 
specimens  far  more  easily  than,  for  example,  specimens 
of  this  last  species  are  from  O.  biennis. 

This  close  familiarity  with  each  form  can  only  be 
attained  by  a  careful  and  minute  study  and  description 
of  all  the  organs  of  the  plant  at  every  stage  of  its  devel- 
opment. Once  a  plant  is  thoroughly  known  in  this  way 
it  can  be  recognized  at  almost  any  stage. 

Varieties  are  distinguished  from  the  mother  species 
usually  by  one  single  character  or  at  most  by  two  or 
three,  whilst  they  resemble  them  in  all  others.  Apart 
from  this  point,  the  difference  between  species  and  vari- 
eties is  to  a  large  extent  arbitrary,  since  when  tested  ex- 
perimentally the  one  is  just  as  constant  as  the  other. 

*And  afterwards  until  now  (Note  of  1908). 


2}i2  The  Pedigree  Families. 

It  is  rather  curious  that  all  the  new  forms  which  have 
arisen  in  my  experiments  should  have  been  species  in  this 
sense  and  not  varieties.  I  have  always  hoped  to  get  a 
white  flowered  form  or  some  other  such  distinct  variety 
but  so  far  in  vain.  O.  nanella  is  perhaps  the  only  form 
which  can  be  called  a  variety  in  the  horticultural  sense 
of  the  term. 

It  is  a  charcteristic  of  varieties  that  they  crop  up  in 
a  great  number  of  unrelated  species,  genera  and  families. 
For  example  the  varieties  rosea,  alba,  laevis,  inermis,  la- 
ciniata,  prolifera,  bracfeata,  and  penditla.  It  is  the  same 
with  monstrosities:  e.  g.,  var :  plena,  fasciafa,  torsa,  ad- 
nata, fissa  and  so  forth.  The  same  is  true  of  dwarfs  or 
the  var.  nana. 

But  with  the  exception  of  O.  nanella  I  cannot  find  in 
other  families  and  genera  any  series  of  forms  analogous 
to  mine.  It  is  for  these  reasons  that  I  do  not  consider 
them  varieties. 

A  very  popular  definition  of  varieties  is  that  they  are 
forms  which  are  known  to  have  arisen  from  other  forms. 
This  position  is  obvious!}^  untenable.  The  proof  of  their 
origin  may  exist  in  the  case  of  some  few  horticultural 
varieties  but  with  the  vast  majority  of  them  and  with 
all  wild  varieties  this  proof  does  not  exist  at  all.  Their 
origin  is  a  thing  of  the  past  and  when,  as  is  usually  the 
case,  it  was  not  witnessed  by  human  eyes  the  so-called 
"proof"  of  it  is  based  on  deduction  or  analogy. 

And  in  all  cases,  where  we  are  not  dealing  with  direct 
observation,  the  origin  of  varieties  is  in  no  sense  what- 
ever more  certain  that  that  of  collective  species  or  genera. 

I  have  dwxlt  on  this  point  because  I  feel  quite  certain 
that  many  of  my  readers  will  regard  my  new  forms  as 


The  Laws  of  Mutation.  253 

varieties  for  the  very  reason  that  I  have  been  able  to  ob- 
serve their  origin.^ 

IV.  New  elementary  species  appear  in  large  numbers 
at  the  same  time  or  at  any  rate  during  the  same  period. 
Scott's  palseontological  results  have  led  him  to  conclude 
that  species-forming  variability,  or,  as  he  also  calls  it, 
mutability  must  appear  simultaneously  in  large  groups 
of  individuals  and  that  the  causes  of  these  changes  have 
probably  been  working  through  long  periods  of  time.^ 

The  palaeontologist  investigates  the  problem  of  the 
origin  of  species  only  in  broad  outline.  It  is  the  experi- 
mental physiologist  who  deals  with  the  separate  individ- 
uals themselves  and  with  their  posterity,  of  whom  not  a 
millionth  part  would  ever  be  preserved  in  the  fossil  state. 
We  have  no  right  therefore  to  expect  more  than  a  general 
agreement  between  the  conclusions  attained  by  these  two 
lines  of  investigation. 

And  when  we  do  find  such  agreement,  as  we  do  in  the 
present  instance,  I  think  it  is  extremely  desirable  that  it 
should  be  put  on  record. 

Amongst  the  species  which  have  arisen  in  my  experi- 
mental garden  Oenothera  gigas  has  only  been  observed 
once.  The  others  appeared  every,  or  nearly  every,  year 
in  varying,  and  often,  indeed,  in  considerable  numbers. 
More  than  800  individuals  of  the  seven  new  species  we 
have  described  arose  independently  from  one  another 
from  the  Laniarckiana-isimiiy.  And  as  about  50,000 
plants  were  cultivated   during  this  period   of   time  the 


^Fortunately,  as  a  matter  of  fact,  this  has  not  been  the  case 
(Note  of  1908). 

^W.  B.  Scott,  On  Variations  and  Mutations.  Amer.  Journ.  Sci.. 
3d  Ser.,  Vol.  48,  No.  287,  Nov.  1894.  See  p.  2>72>-  '"Forces  both  ex- 
ternal and  internal  similarly  afifect  large  numbers  of  individuals." 


254  The  Pedigree  Families. 

number  of  new  forms  amounted  to  between  1  and  2  % 
of  the  total  cultivated. 

In  other  words :  The  new  elementary  species  arose 
from  the  parent  form  in  a  ratio  of  1-2  %.  Sometimes 
more  than,  but  oftener  less  than,  this  value.  And  this 
ratio  was  maintained  throughout  the  whole  course  of 
my  experiment,  so  far,  at  least,  as  the  difference  in  the 
methods  of  investigation  which  have  been  employed  at 
different  times  permit  me  to  estimate  it. 

This  figure,  1-2  %,  is  more  probably  too  small  than 
too  large.  For  it  was  only  in  the  years  1895  and  1896 
that  I  went  to  the  labor  of  determining  it  accurately.  In 
previous  years  the  average  was  considerably  lowered  by 
other  circumstances,  the  most  important  of  which  was 
the  omission  of  such  forms  as  O.  ohlonga,  O.  nihrinervis 
and  O.  scintiUans  which  at  that  time  I  could  not  recognize 
in  their  early  stages.  The  table  on  page  224  shows,  for 
the  two  years  1895  and  1896,  22,000  individuals  of  La- 
marckiana  and  711  of  the  new  forms.  That  is,  more  than 
3  %. 

O.  laevifolia  and  0.  brevistylis  formed  far  smaller 
a  percentage  than  3  %  of  the  number  of  Oenotheras 
growing  on  the  original  field  at  Hilversum ;  yet  they, 
obviously,  arose  in  quantities  sufficient  for  them  to  main- 
tain themselves.  We  may  conclude  therefore  that  a  yearly 
appearance  in  the  proportion  of  from  1  to  3  %  would  be 
sufficient  for  the  establishment  of  a  new  species.^ 

V.  The  nezv  characters  have  nothing  to  do  with  in- 
dividual variability.  Oenothera  Lamarckiana  exhibits  a 
degree  of  fluctuating  variability  in  all  its  characters 
which  is  certainly  not  less  than  that  exhibited  by  other 
plants.     The  new  species  fall  right  outside  the  range  of 

^Compare  the  calculations  of  Delboeuf,  as  given  above  (I  §28). 


The  Laws  of  Mutation.  255 

this  variability;  as  is  evident  from  the  fact  that  they 
are  not  connected  with  the  parent  type  by  intermediate 
or  transitional  forms. 

New  races  can  of  course  be  evolved  by  repeated  selec- 
tion in  one  or  another  direction  in  Lamarckiana  just  as 
much  as  in  any  other  plant.  Indeed  I  have,  myself, 
produced  a  long-fruited  and  a  short-fruited  form  in  this 
way.  But  such  races  remain  dependent  on  selection  and 
differ  from  their  type  only  in  one  feature :  they  do  not 
bear  the  slightest  resemblance  to  elementary  species. 

Elementary  species  themselves  exhibit  fluctuating 
variability,  and  often  indeed  to  a  greater  extent  than  the 
parent  form.  Nearly  all  their  organs  and  characters  vary, 
but  never  in  such  a  way  as  to  approach  the  original  form. 

VI.  The  imitations,  to  zvhich  the  origin  of  new  ele- 
mentary species  is  due,  appear  to  he  indefinite,  that  is  to 
say,  the  changes  may  affect  all  organs  and  seem  to  take 
place  in  almost  every  conceivable  direction.  The  plants 
become  stronger  (gigas)  or  weaker  (albida).  with 
broader  or  with  smaller  leaves.  The  flowers  become 
larger  (gigas)  and  darker  yellow  (rttbrinerz'is),  or 
smaller  (oblonga  and  scijitillans)  and  paler  (albida). 
The  fruits  become  longer  (rubrinervis)  or  shorter  (gi- 
gas, albida,  lata).  The  epidermis  becomes  more  uneven 
(albida)  or  smoother  (laevifolia)  :  the  crumples  on  the 
leaves  either  increase  (lata)  or  diminish  (scintillans). 
The  production  of  pollen  is  either  increased  (rubrinervis) 
or  diminished  (scintillans)  ;  the  seeds  become  larger 
(gigas)  or  sm.aller  (scintillans) ,  more  plentiful  (rubri- 
nervis) or  more  scanty  (lata).  The  plant  becomes  fe- 
male (lata)  or  almost  entirely  male  (brevistylis)  ;  many 
forms  which  are  not  described  here  were  almost  entire!)' 
sterile,  some  almost  destitute  of  flowers. 


256  The  Pedigree  Fain  Hies. 

O.  gigas,  O.  scintillans,  0.  ohlonga  tend  to  become 
biennial  more  than  O.  Lamarckiana ;  and  O.  lata  tends 
to  become  less  so;  whilst  O.  nanella  cultivated  in  the 
usual  way  scarcely  ever  runs  into  a  second  year. 

This  list  could  easily  be  extended,  but  for  the  present 
it  may  suffice. 

To  regard  the  new  forms  from  another  point  of  view, 
some  of  them  are  fitter,  some  unfitter  than  the  parent 
form,  and  others  neither  the  one  nor  the  other.  Until 
experiments  have  been  made  with  the  new  forms  sown  in 
the  field  it  is  obvious  that  no  definite  conclusion  on  this 
point  can  be  arrived  at :  nor  do  the  observations  which 
have  so  far  been  made  on  the  plants  growing  in  the  field 
at  Hilversum  throw  any  light  on  the  subject. 

Nevertheless  it  is  evident  that  the  female  0.  lata  is 
at  a  great  disadvantage;  and  that  0.  albida  with  its  nar- 
row leaves  is,  at  any  rate  in  its  early  stages,  far  too  deli- 
cate. O.  rubrinerz'is  looks  quite  robust  but  is  very  brittle 
and  liable  to  be  broken.  Annual  plants  of  O.  ohlonga 
bear  hardly  any  seeds,  whilst  O.  nanella  is  very  small  and 
its  petioles  are  often  brittle.  All  these  forms  appear  to 
me  to  be  less  fit  as  compared  with  O.  Lamarckiana. 

On  the  other  hand  0.  laevifolia  seems  to  be  at  least 
a  match  for  its  parent;  and  O.  gigas  in  many  respects 
superior  to  it :  all  its  organs  are  larger  and  stronger  and 
apparently  better  adapted  to  perform  their  functions; 
the  whole  plant  is  stouter.  Sowings  of  this  species  in 
the  open  should  give  favorable  results. 

The  forms  which  have  not  yet  been  described  (0. 
spathulata,  suhovata,  etc.)  are  hampered  in  the  struggle 
for  existence  by  their  almost  complete  sterility.  O.  sub- 
linearis  with  its  slender  grass-like  leaves  is  much  too 
weak  in  its  early  stages — and  so  forth. 


The  Laws  of  Mutation.  257 

Many  authors  already  hold  that  species-forming  vari- 
ability must  be  indiscriminate.  We  are  strongly  opposed 
to  the  conception  of  a  definite  ''tendency  to  vary"  which 
would  bring  about  useful  changes,  or  at  least  favor  their 
appearance.  The  great  service  which  Darwin  did  was 
that  he  demonstrated  the  possibility  of  accounting  for  the 
evolution  of  the  whole  animal  and  vegetable  kingdom 
without  invoking  the  aid  of  supernatural  agencies.  Ac- 
cording to  him  species-forming  variability  exists  without 
any  reference  to  the  fitness  of  the  forms  to  which  it  gives 
rise.  It  simply  provides  material  for  natural  selection 
to  operate  on.  And  whether  this  selection  takes  place 
between  individuals,  as  Darwin  and  Wallace  thought, 
or  whether  it  decides  between  the  existence  of  whole  spe- 
cies, as  I  think ;  it  is  the  possibility  of  existence  under 
given  external  conditions  which  determines  whether  a 
new  form  shall  survive  or  not. 

We  can  go  a  step  further  and  say  that  many  more 
useless  and  unfavorable  variations  must  arise  than  favor- 
able ones.  This  becomes  sufficiently  evident  when  we 
consider  the  complexity  of  the  conditions  which  an  organ- 
ism has  to  satisfy  before  it  can  supplant  its  fellows. 

The  mutability  of  Oenothera  Laniarckiana  satisfies 
all  these  theoretical  conditions  perfectly.  Nearly  all  or- 
gans and  all  characters  mutate,  and  in  almost  every  con- 
ceivable direction  and  combination.  Many  combinations 
must  obviously  be  fatal  to  the  life  of  the  germ  within  the 
ripening  seed  and  cannot  on  that  account  be  observed. 
Others  hinder  the  development  of  the  seedlings  and  wdiole 
series  of  experiments  with  apparently  mutated  plants 
came  to  nothing  in  spite  of  every  care  on  account  of  the 
premature  death  of  the  young  plants.  Many  combina- 
tions reduce  the  fertilitv  so  much  that  we  cannot  jro  fur- 


258  The  Pedigree  Fainilies. 

ther  than  observe  the  mutated  individual  itself.  A  num- 
ber of  other  combinations  are,  I  suppose,  lost  in  my  ex- 
periments because  they  cannot  be  detected  until  the  plants 
are  fairly  old,  by  which  time  the  great  majority  have  been 
weeded  out  to  make  more  room.^  Such  considerations 
seem  to  me  to  explain  how  it  was  that  I  was  able  to  cul- 
tivate only  so  small  a  number  of  new  species  through 
more  than  one  generation.  And  it  is  of  course  open  to 
question  how  many  of  those  that  I  did  cultivate  could 
survive  the  struggle  for  existence. 

I  conclude  therefore :  Mutability  is  indiscriminate. 
Some  mutations  bear  no  offspring  and  disappear  forth- 
with. Between  the  others  and  the  species  already  estab- 
lished natural  selection  must  decide,  unless  artificial  se- 
lection steps  in. 

VII.  MufabUity  appears  periodically.  I  am  led  to 
this  conclusion  by  my  experiments ;  but  I  express  it  at 
present  only  tentatively.  The  fact  that  of  all  the  species 
that  I  have  examined  so  far,  only  one  has  proved  to  be 
in  a  state  of  mutation  appears  to  me  sufficient  evidence 
for  this  conclusion.  But  further  investigations  are  neces- 
sary for  the  establishment  of  the  generalization :  and 
such  I  have  only  recently  started.  I  am  not  of  course 
now  in  a  position  to  give  experimental  proof  of  the 
existence  of  mutable  and  immutable  periods :  but  I  have 
enunciated  the  hypothesis  of  their  existence  as  the  sim- 
plest explanation  of  the  remarkable  fact  that  I  have  so 
far  observed  mutations  only  in  a  single  species ;  though 
plentifully  enough  in  it. 

The  above  generalizations  refer  in  the  first  instance 
to  the  case  which  we  have  observed,  namely  the  muta- 

*  For  example  O.  brevistylis  and  O.  leptocart<a  are  not  recogni- 
zable until  just  before  they  flower. 


A  Branch  of  the  Lamarckiana-Fainily.  259 

bility  of  Oenothera  Lamarckiana.  But  inasmuch  as  ex- 
perimental investigation  of  other  instances  has  not  yet 
been  pubHshed,  we  must,  pending  the  acquisition  of  that 
knowledge,  regard  it  as  a  typical  case  of  the  origin  of 
new  species. 


§  5.    A  BRANCH  OF  THE  LAMARCKIANA-FAMILY. 

In  1895  I  started  a  culture  which  may  be  res^arded 
as  a  branch  of  the  main  line  of  descent  which  has  already 
been  described.  My  object  was  to  try  to  get  more  muta- 
tions by  increasing  the  sowings.  I  used  the  seed  which 
had  been  harvested  in  1889,  a  part  of  which  had  already 
been  employed  in  the  culture  summarized  on  p.  224. 
The  available  quantity  of  seed  amounted  to  about  230 
ccm.  and  was  all  sown. 

In  November  1888  I  picked  out  from  among  the 
plants  that  I  had  saved  during  the  summer  the  12  strong- 
est; and  planted  them  on  a  separate  bed  where  the  con- 
ditions were  very  favorable  owing  to  the  fact  that  the 
position  was  a  sunny  one,  and  that  it  was  far  away  from 
any  other  Oenothera  cultures.  In  the  spring  of  1889  I 
reduced  the  number  to  6,  which  grew  up  to  fine  well- 
branched  plants.  Each  plant  flowered  not  only  on  its 
main  stem  and  its  branches  but  also  on  the  numerous 
branches  which  sprang  from  the  axils  of  the  radical 
leaves.  Superfluous  lateral  branches  were  however  cut 
away  in  July.  Each  plant  furnished  from  25-50  ccm. 
of  seed  and  the  seed  from  separate  plants  was  harvested 
separately.  The  pollination  of  the  flowers,  which  were 
not  enclosed,  was  left  to  insects.  I  sowed  the  seed  as 
evenly  as  possible  on  a  bed  of  12  square  meters,  kee])ing 
the  seed  of  the  6  seed-parents  in  separate  lots.     As  soon 


260  The  Pedigree  Families. 

as  the  young  seedlings  were  identifiable  they  were  re- 
corded and  removed.  Those  which  bore  the  characters 
of  their  parents  were  simply  pulled  up  and  thrown  away 
with  the  exception  of  some  which  did  not  interfere  with 
the  growth  of  their  neighbors  and  could  therefore  be 
allowed  to  flower.  The  mutants  were  always  carefully 
removed  and  planted  singly  in  pots  with  rich  garden-soil 
for  further  experiment.  This  sorting  lasted  from  the 
middle  of  May  till  the  middle  of  June. 

The  lata  and  nanella  plants  were  recognizable  at  a 
very  young  stage  and  so  could  be  transplanted  in  large 
numbers  before  they  became  overshadowed  and  over- 
grown by  the  plants  which  surrounded  them. 

The  same  was  true  of  alhida  which  was  however  al- 
ways very  delicate.  Not  until  a  much  later  stage  of 
growth  was  oblonga  recognizable ;  and  later  still  rubri- 
nervis.  At  this  time  the  bed  was  thickly  covered  with 
the  rosettes,  the  stronger  ones  overgrowing  the  weaker 
ones.  There  can  be  hardly  any  doubt  that  many  mutants 
especially  of  the  riihrinervis  and  the  other  rare  types  per- 
ished in  this  way  before  I  was  able  to  recognize  and  trans- 
plant them.  Therefore  the  figures  given  underestimate 
rather  than  overestimate  the  actual  number  of  mutants. 

About  the  middle  of  June  the  plants  were  so  crowded 
that  there  was  no  longer  any  hope  that  any  particularly 
late  mutant  could  maintain  itself.  I  then  simply  thinned 
them  out  as  much  as  was  necessary  to  give  those  that  re- 
mained room  to  flower.  In  August  about  700  plants 
flowered.  Later  on  two  of  these  attracted  attention  b}^ 
the  great  length  of  their  stems  which  were  much  longer 
than  those  of  the  rest  and  towered  above  them.  Thev 
turned  out  to  be  a  new  form  which  has  appeared  again 
in  other  strains  and  will  be  termed  O.  Icptocarpa.     Apart 


A  Branch  of  the  Lamarckiana- family.  261 

from  these  the  beds  contained  nothing  but  pure  0.  La- 
marckiana:  I  examined  them  repeatedly  and  thoroughly 
during  the  whole  time  that  they  were  in  flower. 

I  harvested  the  seed  in  October  and  took  care  that  as 
few  as  possible  fell  to  the  ground ;  for  it  still  contained 
a  good  deal  of  seed  from  the  original  sowing  which  I 
expected  to  germinate  in  the  following  spring. 

I  had  already  become  acquainted  with  this  belated 
germination  in  one  particular  case.  In  March  1887  I 
sowed  some  thousands  of  seeds ;  they  germinated  during 
the  course  of  the  whole  summer  and  at  the  end  of  each 
month  the  seedlings  were  counted  and  pulled  up.  Up  to 
the  middle  of  April  908  germinated ;  between  then  and 
the  middle  of  May  288.  From  the  14th  of  May  to  the 
14th  of  July  only  64  germinated:  from  then  till  the  14th 
of  September  130;  and  between  that  date  and  the  middle 
of  October  only  6.  During  the  winter  there  was  no  ger- 
mination although  the  sowing-pans  were  protected  from 
the  frost  and  the  circumstances  were  favorable  in  every 
other  way.  Up  till  the  middle  of  March  1888  there  ap- 
peared only  three  seedlings.  But  then — in  the  second 
spring  —  an  extraordinarily  large  number  appeared.-^ 
Within  14  days  272  plants  had  unfolded  their  leaves,  and 
others  followed  as  before  in  gradually  decreasing  num- 
bers. The  latest  seeds  stayed  for  2  or  more  years  in  the 
ground  before  they  germinated. 

In  the  spring  of  1896  therefore  I  expected  the  seeds 
which  had  remained  in  the  ground  from  the  previous 
spring  to  germinate.  Whilst  this  was  taking  place  I 
counted  the  mutants  and  transplanted  them  singly  into 
pots  as  before ;  I  weeded  out  the  normal  individuals  as 

^  A  similar  phenomenon  is  known  to  occur  in  the  case  of  species 
of  clover,  Primula  and  many  other  plants. 


262 


Jlte  Pedigree  Fainilies. 


early  and  as  completely  as  possible,  without  counting 
them.  I  found,  altogether,  102  mutants  but  in  quite 
different  proportions  to  that  in  which  they  appeared  in 
the  previous  year.  Particularly  was  this  the  case  with 
albida  and  lata  which  were  very  rare  and  with  rnbri- 
nervis  which  was  relatively  plentiful. 

I  shall  now  display  the  result  of  this  experiment  in 
the  form  of  a  genealogical  table  similar  to  that  on  page 
224.  The  two  parts  of  the  last  generation  which  appeared 
in  the  two  successive  years  are  entered  separately. 


OENOTHERA  LAMARCKIANA. 

A 

THE  LAMARCKIANA-FAMILY. 

II 
TABLE  TO  SHOW  THE  ORIGIN  OF  NEW  SPECIES  IN  A  BRANCH 

OF  THE  MAIN  CULTURE. 

(The  figures  refer  to  the  numbers  of  individuals.) 


^"^  T^ffcTT"*  T**      •    rr^~r  J'^'^'^  C\ 

SPECIES 

GEJSERATIOrsS     \ 

1 

1 

i 

albida 

Oh- 
io ng-a 

rubri- 
nervis 

O.     1    na- 
Lam.    nella 

lata 

1  scin- 
tillans 

elHpti- 
ca 

lepto- 
carpa 

3rd  gen. 

second 

1 

1 

year 

III  B 

1896 
first  year 

1 

54        8         —          35         3 

0          1 

0 

III  A 

1895 
2nd  gen. 

255 

69        1     10,000    111     168 

1          7 

2 

~-~-~                                       — ^ 

(biennial) 

II 

1888-1889 

1 

6 

1st  gen. 

(biennial) 

I 

1886-1887  i 

C 

) 

A  Branch  of  the  Lamar ckiana-Family.  263 

The  whole  number  of  mutants  in  the  year  1895 
amounted  therefore  to  614  or  about  6  %,  of  which  0. 
albida  made  up  2.5  %,  O.  lata  1.7  %,  O.  nanella  1.1  %, 
O.  oblonga  0.7  %  and  the  rest  altogether  0.1  %.  I  have 
not  calculated  the  percentages  of  mutants  for  the  year 
1896,  in  which  102  occurred. 

The  figures  show  a  very  good  agreement  with  those 
which  will  be  found  in  the  table  on  page  224.  There  are 
of  course  divergences  of  detail,  as  is  only  to  be  expected. 
But  similar  divergences  were  also  found  between  the 
numbers  produced  by  the  6  different  plants.  I  have  not 
thought  it  worth  while  to  give  these  here  in  detail ;  suffice 
it  to  say  that  the  commoner  mutants  occurred  in  each  of 
the  six  sowings  though  in  varying  proportions. 

One  of  these  six  sowings  gave  a  highly  unexpected 
and  interesting  result.  It  was  the  most  extensive  one ; 
75  ccm.  of  seed  was  sown  on  4  square  meters  of  soil ; 
that  is  to  say  as  much  per  square  meter  as  for  the  5  other 
plots.  These  seeds  did  not  do  at  all  well.  In  1895  only 
350  germinated  that  is  5  per  cubic  centimeter,  whereas 
usually  70  per  cubic  centimeter  germinated.^  These  350 
seeds  gave  rise  to  the  number  of  mutants  shown  in  col- 
umn A. 

Number  of  mutants  per  4  square  meters. 

A  B 

O.  albida 64  95 

O.   oblonga   9  30 

O.   rubrinervis    .  .  1  0 

0.   nanella     0  5S 

O.  lata    61  54 

Totals 135         234 

^  A  cubic  centimeter  contains  about  500  seeds. 


264  The  Pedigree  Families. 

For  comparison  I  give  in  column  B  the  mutants  pro- 
duced by  the  five  other  mothers  per  similar  area  under 
cultivation  or  per  4  square  meters. 

If  we  reckon  the  percentage  of  mutants  among  the 
seedlings  derived  from  this'  particular  mother  we  find  it 
to  be  about  40  %  instead  of  the  6  %  of  the  wdiole  culture 
(or  the  5  %  of  the  5  other  mother  plants). 

But  if  we  calculate  this  figure  per  cubic  centimeter 
of  seeds  we  find  it  to  be  for  this  plant  1.8,  but  for  the 
rest  3.2. 

The  absolute  total  of  mutants  is  therefore  reduced  to 
one-half  through  failure  to  germinate,  wdiilst  the  absolute 
number  of  seeds  that  germinated  w^as  reduced  from  70 
to  5  per  cubic  centimeter.  The  percentage  of  mutants 
from  the  seeds  which  did  germinate  rose,  therefore,  from 
5  to  40  %. 

The  failure  to  germinate  was  in  all  probability  due 
to  the  fact  that  the  seed  had  been  kept  for  5  years ;  but  it 
is  difficult  to  see  why  this  should  have  affected  one  sample 
of  seed  and  not  the  five  others.  When  seeds  are  kept 
they  gradually  die  off,  some  sooner,  some  later. 

It  follows  from  the  facts  described  above  that  mu- 
tating seeds  do  not  die  off  so  soon  as,  or  remain  capable 
of  germinating  longer  than  normal  Lamarckiana  seeds. 
It  is  only  the  seeds  of  the  dwarf  form  that  appear  w^eaker 
than  the  parent  species  and  perhaps  also  those  of  O. 
clliptica. 

Should  this  phenomenon  prove  to  be  a  general  one 
it  should  be  possible  by  artificially  hastening  the  death 
of  the  seeds  to  materially  increase  the  percentage  of 
mutants  in  a  given  sample.  Such  a  discovery  would  im- 
mensely facilitate  the  search  for  mutations  in  the  vege- 
table kingdom. 


The  Laevifolia-Family.  265 

I  must  now  return  to  the  transplanted  seedlings.  Sev- 
eral of  them  were  weak,  and  died  sooner  or  later ;  espe- 
cially the  most  easily  recognizable  of  them  all,  O.  albida. 
In  the  case  of  others  too  many  were  raised  for  them  all 
to  flower.  But  I  grew  the  majority  of  them  during  the 
whole  summer;  some  of  them  flowered;  others  remained 
in  the  rosette  stage.  I  saved  seeds  from  O.  albida  in  1897 
(from  plants  which  came  up  in  1896)  from  0.  ntbri- 
nervis,  O.  nanella  and  O.  scintillans.  The  first  three 
when  self-fertilized  bred  true,  the  last  did  not  (see  page 
244).  Further  details  on  this  point  will  be  given  in  the 
second  chapter  under  the  heading  of  the  plant  in  ques- 
tion. 

§  6.    THE  LAEVIFOLIA-FAMILY. 

In  1887,  I  noticed  in  the  locality  for  Oenothera  La- 
marckiana  near  Hilversum,  a  group  of  individuals  whose 
peculiar  characters  showed  them  to  be  a  distinct  form. 
I  therefore  gathered  some  of  their  seeds  and  sowed  them 
in  the  following  year  in  my  experimental  garden.  The}^ 
gave  rise  to  two  forms  (as  was  to  be  expected  from  the 
fact  that  no  attempt  was  made,  or  was  possible,  to  insure 
self-fertilization)  of  which  the  one  was  the  ordinary 
Lamarckiana  whilst  the  others  were  like  the  parent  plant. 
T  propose  to  call  this  subspecies  O.  laevifoUa  on  account 
of  its  smooth  leaves  which  are  not  or  at  any  rate  scarcely 
perceptibly  crumpled,  as  is  the  case  in  Lamarckiana. 

For  the  first  few  years  I  let  the  two  forms  grow  and 
flower  together  and  took  no  further  precaution  than  iso- 
lating them  from  the  rest  of  the  cultures.  In  the  year 
1894  I  began  the  practice  of  enclosing  the  1)lossoms  be- 
fore opening  in  paraflined  paper  bags  and  of  fertilizing 


266  The  Pedigree  Families. 

them  with  their  own  pollen.  They  have  since  that  time 
bred  true  and  given  rise  to  no  more  0.  Lainarckiana; 
nor  have  they,  since  that  time  given  rise  to  any  muta- 
tions. 

How  and  when  O.  laevifolia  arose  I  do  not  of  course 
know.  It  was  already  there  when  I  visited  the  locality 
for  the  first  time.  But  it  grew  there  in  a  special  isolated 
spot  in  such  a  way  as  to  make  it  probable  that  the  plants 
had  grown  from  the  seeds  of  a  single  parent  which  we 
must  suppose  had  arisen  there  not  so  very  long  before. 
I  propose,  therefore,  to  give  a  somewhat  detailed  de- 
scription of  the  original  locality.  I  shall  have  frequent 
occasion,  when  I  shall  be  describing  other  families  or 
individual  species,  of  referring  to  it  again. 

■■  On  the  estate  of  Jagtlust,  the  property  of  Dr.  juris 
J.  Six,  between  Hilversum  and  's  Graveland  in  the 
Netherland  province  of  North  Holland  there  was  at  one 
time  a  potato  field,  whose  southern  boundary  bordered 
on  a  canal  which  had  been  dug  many  years  before.  About 
the  year  1870  the  owner  had  a  new  branch  of  this  canal 
dug  which  followed  the  western  boundary  of  the  field, 
and  completely  shut  off  any  access  to  it  from  the  north. 
So  that  the  field  became  accessible  only  from  the  east 
where  there  was  no  road ;  and  it  consequently  became  im- 
possible to  let  it.  From  that  time  it  lay  fallow;  and  in 
the  first  few  years  was  not  dug  any  more  than  was  neces- 
sary for  the  laying  of  a  few  paths  and  the  planting  of 
a  few  trees.  It  obviously  afforded  wild  plants  a  splendid 
opportunity  of  almost  unlimited  multiplication.  Oeno- 
thera had  seized  this  opportunity  somewhat  later  than  the 
other  wild  plants  in  the  neighborhood  and  although  it 
did  not  spread  as  fast  as  they,  it  took  fuller  advantage 
of  the  field  in  the  end. 


The  Laevifolia-F amily .  267 

Near  the  field,  there  was  a  small  heel  in  a  park  in 
which  some  annuals  were  grown  every  year.  Amongst 
these  was  Oenothera  Lamarckiana  which  spread  from 
this  spot  over  the  field.  When  I  first  visited  the  place 
the  little  bed  had  long  since  run  wild,  but  was  still  recog- 
nizable. The  Oenotheras  were  most  numerous  on  the 
northeast  corner  of  the  field,  close  to  the  bed  they  spread 
from.  Here  they  formed  a  dense  jungle  of  branched 
stems  as  high  as  a  man.  The  area  of  the  whole  field  vv^as 
about  5000  square  meters. 

This  dense  group  was  surrounded  by  a  broad  zone 
of  plants  a  few^  of  which  were  in  flower,  and  of  numerous 
rosettes,  growing  together;  whilst  to  the  west  of  this 
*  zone  only  isolated  rosettes  were  to  be  found.  But  on  the 
greater  part  of  the  field  not  a  single  Oenothera  was  to  be 
seen  at  first  glance ;  though,  after  further  search  I  found 
flowering  plants  in  two  places,  and  in  five  or  six  other 
places  rosettes  with  radical  leaves,  evidently  from  seed 
which  had  germinated  that  spring. 

We  may  conclude  therefore  that  the  plants  began  to 
spread  from  the  northeast  corner  of  the  field  in  the  period 
1884  to  1886.  In  1888  the  whole  field  had  become  occu- 
pied by  isolated  groups  consisting  of  both  young  and 
two-vear-old  flowerins^  individuals. 

In  the  winter  1886-7  and  1887-8  a  part  of  the  north- 
east corner  of  the  field  comprising  more  than  one-half 
of  the  Oenothera  patch  was  deeply  dug  and  planted  with 
oaks.  But  the  ground  was  so  full  of  seed  that  for  two 
summers  afterwards,  this  piece  was  thickly  covered  with 
rosettes  and  flowering  plants  of  Oenothera.  One  result 
of  this  was  a  very  high  degree  of  variability  in  the  dura- 
tion of  life  of  the  plants,  for  there  could  be  seen  on  this 
spot  during  the  month  of  August  and  September  numer- 


268  The  Pedigree  Families. 

ous  stems  of  every  conceivable  height  between  rosettes 
which  had  not  yet  developed  a  stem  and  tall  flowering 
plants. 

In  1889  the  owner  of  the  property,  having  decided  to 
plant  the  rest  of  the  field  with  trees/  had  two  straight 
paths  made,  intersecting  each  other,  and  a  semicircular 
path  to  round  oft  that  side  of  the  field  which  did  not 
abut  on  tlie  canals.  On  both  sides  of  these  paths  the 
ground,  which  is  almost  pure  sand,  was  dug  up  to  a 
depth  of  three  or  four  feet  and  planted  with  young  trees. 
Many  Oenotheras  were  of  course  destroyed  in  this  way, 
but  since  that  time  they  have  spread  more  rapidly  than 
ever.  The  newly  turned  soil  seemed  to  suit  them;  for 
they  grew  on  it  in  the  most  extraordinary  profusion  and 
extended  from  it  in  all  directions  over  the  whole  field 
w^hose  easterly  half  they  had  almost  completely  covered 
bv  1894. 

It  is  more  than  natural  that  from  such  a  center  the 
plant  should  have  gradually  spread  in  the  neighborhood. 
As  early  as  1888  I  found  it  in  one  or  two  fields  a  good 
way  off,  and  since  then  it  has  occurred  elsewhere ;  but 
always  in  relati\Tly  small  numbers. 

As  soon  as  I  had  become  acquainted    (1886)    w^ith 

the  spot  in  question  on  the  deserted  potato  field  I  saw 

that  here  was  a  wonderful  opportunity  of  getting  some 

insight  into  the  phenomena  of  variation  as  exhibited  by 

a  plant  which  was  multiplying  rapidly.     The  diversitv 

in  the  form  of  the  leaves,  the  height  of  the  stem  and  the 

mode  of  branching  etc.  exhibited  a  very  high  degree  of 

variability,   and  when  the   large  bright  yellow   flowers 

opened  in  July  and  August  I  saw  that  almost  every  single 

^  In  consequence  of  this  the  field  is  now  entirely  covered  with 
wood,  partly  consisting  of  oak  and  partly  of  pines,  leaving  hardly  any 
room  for  Oenotheras  to  grow.     (Note  of  1908.) 


The  La evifolia- Family.  269 

character  was  highly  variable.  A  whole  series  of  varia- 
tions in  the  flowers  not  hitherto  described  for  this  spe- 
cies, was  found  in  the  first  few  days  and  many  more  of 
them  were  noticed  when  I  visited  them  later. 

In  1886,  1887  and  1888  I  spent  the  whole  summer 
at  a  spot  a  few  minutes  walk  from  the  field  and  so  had 
the  opportunity  of  studying  this  single  species  for  hours 
at  a  time  every  week  and  often,  even,  every  day.  Since 
then  I  have  visited  the  place  nearly  every  year,  often 
indeed  twice  or  oftener,  every  year ;  or  I  have  had  ac- 
counts of  it  from  others ;  so  that  I  have  been  able  to  fol- 
low the  progress  of  events  step  by  step  by  collecting  ac- 
counts of  the  behavior  of  old  mutations,  and  of  the 
origin  of  new  ones  on  the  field. 

But  it  soon  became  evident  that  to  follow  the  se- 
quence of  events  more  closely  the  investigation  must  be 
continued  on  the  lines  of  experimental  culture.  Mr. 
Six  kindly  agreed  to  my  taking  some  first  year  rosettes 
and  seed  from  the  field.  My  object  in  doing  this  was 
twofold.  In  the  first  place  (we  will  suppose  for  the  mo- 
ment that  we  are  justified  in  regarding  the  deviations 
exhibited  by  an  individual  as  already  present  in  the  seed 
which  produces  it)  we  learn  by  sowing  in  the  garden 
the  seed  gathered  in  the  field,  in  a  far  more  certain  and 
precise  manner,  what  new  forms  would  be  produced  in 
the  field.  In  the  second  place  I  have  saved  seed  from 
the  plants  thus  raised  in  the  garden  and  have  sown  them 
and  have  in  this  way  raised  the  different  "Families"  each 
of  which  has  its  origin  on  the  field  at  Hilversum,  and 
has,  in  great  part,  repeated  the  process  of  mutation  under 
daily  control  in  my  experimental  garden.  It  is  evident 
that  in  this  wav  a  much  more  accurate  investis^ation  of 
heredity  was  made  possible  than  could  ever  ha\'e  been 


270  The  Pedigree  Families. 

carried  out  in  the  field.  Of  such  families  I  possess  three, 
as  I  have  already  stated.  The  Laniarckiana-i2im\\y  arose 
from  rosettes,  the  /a/a-family  from  seeds  gathered  in 
1886,  and  the  laevifolia-i^mxXy,  with  which  this  section 
deals,  from  the  small  group  of  that  species  that  was 
found  in  the  field  (1887).  The  hereditary  phenomena 
which  they  exhibited  afforded  a  clearer  insight  into  these 
processes  than  could  be  derived  from  the  observations  in 
the  original  locality. 

I  propose  to  ofTer  now  some  remarks  on  the  incom- 
pleteness of  field-observations  and  on  some  difficulties 
of  experimenting  in  a  garden.  If  every  mutation  was 
a  favorable  one  and  gave  rise  to  individuals  which  had 
a  good  chance  of  surviving  in  the  struggle  with  their 
neighbors  in  the  field,  and  with  unfavorable  climatic 
conditions  in  the  cultivated  state,  many  a  new  form 
would  have  come  under  observation,  which,  as  it  is,  must 
have  perished  in  its  youth.  But  most  new  species  are 
weaker  than  their  parent,  for  example  by  having  smaller 
leaves,  and  therefore  grow  more  slowly ;  some  are  partly 
or  absolutely  sterile  in  one  sex  and  therefore  cannot  be 
perpetuated  at  all  except  by  crossing;  whilst  others  come 
to  nought  for  unknown  reasons. 

Variability  in  the  duration  of  life  is  especially  un- 
favorable ;  and  may  become  positively  dangerous  in  cul- 
tivation. Normal  annual  and  biennial  individuals  can 
be  easily  made  to  flower  and  to  set  seed,  although  in- 
ability to  resist  cold  has  been  the  cause  of  the  loss  of 
some  of  my  most  interesting  rosettes.  On  the  other  hand 
there  often  occur  plants  which  behave  as  if  they  were 
going  to  be  annual  but  grow  their  stem  too  late  to  set 
seed  or  even,  in  many  cases,  to  flower  at  all,  before  they 
are  carried  off  by  the  winter.     In  the  case  of  several  of 


The  Laez'ifolia-Fainil\.  271 

my  new  species  it  was  not  until  many  years  had  elapsed 
that  I  succeeded  in  getting  them  to  flower  and  ripen  their 
fruits — as  for  example  O.  albida  and  O.  elliptica. 

I  must  now  return  to  O.  laevifolia.  I  found  it  first 
in  1887  when  I  came  across  ten  specimens  which  coukl 
be  recognized  as  a  new  type  by  the  oval,  as  opposed  to 
heart-shaped,  petals  of  the  flowers  of  their  lateral 
branches. 

Five  of  these  plants  formed  the  nucleus  of  a  little 
group  of  about  a  hundred  individuals  which  stood  in  the 
northwest  part  of  the  field  far  removed  from  any  other 
Oenotheras.  In  the  previous  year  I  had  seen  on  this  spot 
some  first  year's  rosettes,  but  no  flowering  plants.  At 
greater  and  lesser  distances  from  this  center  there  grew 
five  other  plants  in  rather  isolated  positions  in  the  field 
which  was  still  poor  in  Oenotheras  in  this  region. 

In  the  following  year  I  found  this  type  in  the  same 
spot  but  not  elsewhere. 

Since  that  time  0.  laevifolia  has  maintained  itself 
on  the  field  in  such  a  way  that  the  original  spot,  which 
was  easily  recognizable  by  certain  features,  has  continued 
to  form  the  nucleus  of  the  whole  group.  In  subsequent 
years  I  have  found  the  species  in  other  parts  of  the  field 
also — but  as  rare  and  isolated  examples  only.  The  num- 
bers of  it,  however,  on  the  original  spot  have  graduall\- 
if  slowly  increased;  the  group  consists,  doubtless  as  the 
result  of  mixed  fertilization  by  insects,  partly  of  0. 
laevifolia  and  partly  of  O.  Lainarckiana.  Since  1894 
that  part  of  the  field  has  been  completely  overgrown  with 
Oenotheras  so  that  the  limits  of  the  original  group  have 
disappeared. 

This  m.ode  of  distribution  of  our  plant  round  a  defi- 
nite center  for  a  period  of  eight  years  coupled  with  the 


272  The  Pedigree  Families. 

fact  that  it  was  allowed  to  cross  freely  with  the  parent 
species  clearly  indicate  the  operation  of  some  definite 
hereditary  process.  Whether  the  ten  plants  of  the  first 
year  (1887)  had  a  common  origin  cannot  of  course  be 
decided  a  posteriori,  but  it  cannot  be  regarded  as  other 
than  extremely  probable. 

I  now  come  to  the  cultures  in  my  experimental  gar- 
den For  these  I  collected,  as  I  have  already  said,  the 
seeds  of  some  examples  of  O.  laevifolia  in  the  field  at 
Hilversum  towards  the  end  of  the  summer  of  1887. 

These  seeds  produced  in  my  garden  in  1888  over 
200  plants  of  which  about  60  %  were  annual ;  some  of 
them  were  O.  Lamarckiana  and  some  O.  laevifolia.  I 
selected  the  seed  from  the  strongest  and  most  precocious 
examples  of  the  crop  for  the  cultivation  of  the  family, 
keeping,  of  course,  the  two  species  separate. 

In  1889  three  beds  of  10  square  meters  were  sown 
with  the  seeds  of  the  0.  Lamarckiana  plants  partly  in 
the  hope  of  getting  new  forms  and  partly  with  a  view  to 
an  investigation,  to  be  described  later  on,  into  the  con- 
ditions determining  the  annual  or  biennial  habit. 

Like  the  two  other  extensive  sowings  in  the  La- 
inarckiana-iRmily  this  one  also  proved  to  be  rich  in  mu- 
tants. I  wish^to  call  especial  attention  to  this  fact  be- 
cause I  believe  that  the  relative  scarcity  of  mutants  in  the 
other  branches  of  this  family  can  be  attributed  to  the 
small  extent  of  the  individual  generations  in  these  cul- 
tures. 

I  got  altogether  41  mutants  whose  appearance  in  the 
various  years  and  cultures  I  shall  now  put  in  the  form  of 
a  genealogical  table.  This  is  constructed  on  exactly  the 
same  plan  as  the  previous  ones. 


The  Laevifolia-Family. 


171 


OENOTHERA  LAAIARCKIANA. 

B 

THE  LAEVIFOLIA-FAMTLY. 

TABLE  EXHIBITING  THE  ORIGIN  OF  NEW   SPECIES  FROM 

O.    LAEVIFOLIA. 

(The  figures  refer  to  the  number  of  individuals.) 


GENKRATIONS 


O. 
laevi- 
folia 


MUTANTS 


lata 


ellip- 
tica 


na-    !  rubri- 
nella  inervis 


spa- 
thu- 
lata 


lepto- 
carpa 


O.  La- 

mar- 

ckia- 

na 


IX 


9th   generation 
1895 

8th   generation 
1894 


VIII ; 

VIII;  1894 

1 

7th   generation 


VII 


1893 


i6th  generation 

Vll  1892 

5th  generation 

V!  1891 


IV 

III 

U 

1 


4th  generation 
1890 

3rd  generation 

1889 

2nd  generation 
1888 

1st  generation 

Hilversum 

1886-1887 

(biennial) 


1500       2         1         0 


53 

I 
25 

8 

2 


12 


44 

i 
96 


400 


N.  B.   The  numbers  composing  the  generations  marked  with  a 
were  not  counted. 


274  The  Pedigree  Families. 

Let  us  now  examine  the  origin  of  the  various  new 
species  in  this  family  a  httle  more  closely.  We  will  begin 
with  the  1889  crop.  It  comprised  about  400  specimens  of 
Lamar ckiana  and  two  rosettes  and  one  annual  plant  of 
O.  lata.  But  as  I  already  had  this  species  under  cultiva- 
tion I  did  not  save  them.  Besides  this,  there  were  two  ro- 
settes of  O.  elliptica  and  two  others  of  a  new  form,  O. 
spathiilata,  which  however  I  did  not  succeed  in  winter- 
ing. Dwarfs  were  fairly  plentiful  in  this  crop;  two  of 
them  developed  stems  but  did  not  succeed  in  flowering; 
ten  remained  in  the  rosette  stage  but  only  two  of  them  sur- 
vived the  winter.  These  formed  the  stock  of  -a  nanella- 
family  of  which  I  have  cultivated  five  generations,  which 
will  be  described  later  (§  18).  One  of  the  dwarfs  that 
appeared  in  1889  had  the  narrow  leaves  of  0.  elliptica 
but  was  a  nanclla  in  every  other  respect.  It  remained  in 
the  rosette  stage  but  died  during  the  winter. 

Besides  the  mutations  we  have  already  named  there 
occurred  in  the  1889  crop  two  examples  of  an  entirely 
new  form,  0.  ruhrinervis.  One  of  them  stayed  in  the  ro- 
sette stage  and  could  not  be  wintered ;  the  other  devel- 
oped a  fine  stem  very  early,  bore  a  profusion  of  flowers 
which  were  however  not  enclosed  in  bags,  and  set  a 
quantity  of  seed  which  was  harvested  on  the  8th  of  Oc- 
tober 1889. 

These  seeds  were  sown  on  the  5th  of  May  1890  on 
a  small  bed.  The  red-veined  individuals  were  distinctly 
recognizable  very  soon  after  the  seeds  came  up,  and  the 
rest  were  destroyed.  In  September  I  had  forty  speci- 
mens of  ruhrinervis  of  which  nine  flovv^ered  and  set  seed. 
The  rest  were  either  annual  but  not  adult,  or  rosettes. 

The  seed  saved  in  1890  was  used  in  1891  partlv  for 
a  culture  on  almost  barren  sand  and  partly  for  a  control 


i 


The  Laevifolia-Fam  ily. 


:/o 


culture  on  good  soil.  I  allowed  the  latter  only  to  flower 
and  at  the  beginning  of  September  chose  the  thirteen  best 
specimens  with  red  spotted  calyces  and  red  blush  on  the 
stalk,  as  seed-parents. 

Since  that  time  this  species  has  maintained  its  char- 
acters. It  has  been  left  to  pollinate  itself  and  crossing 
has  not,  or  has  scarcely  ever,  occurred.  Later,  it  was  used 
for  the  development  of  a  tricotylous  race  by  weeding  out 
all  specimens  which  did  not  exhibit  tricotyly.  0.  riibri- 
ncrvis  proved  also  to  be  almost  completely  annual,  if 
suitably  cultivated.  In  the  first  two  years  during  which 
they  were  selected  for  tricotyly  the  30-60  individuals 
which  were  raised  gave  rise  to  no  mutants  which  need 
be  mentioned  here,  but  in  1894  there  appeared  among  the 
tricotylous  forms  two  examples  of  lata,  both  of  which 
were  annual  and  managed  to  flower ;  after  which  they 
were  removed  from  the  bed. 

Since  1894  I  have  always  enclosed  the  flowering 
spikes  of  the  stock  plants,  i.  e.,  plants  which  are  chosen 
to  provide  seed  for  growing  the  next  generation,  in 
parchment  bags  and  have  artificially  fertilized  them  with 
their  own  pollen  in  order  to  obtain  definite  proof  of  their 
constancy.  It  should  be  mentioned  here  that  before  this 
time  these  strains  exhibited  a  very  high  degree  of,  though 
not  an  absolute,  constancy.  All  that  was  necessary  to 
show  this  was  to  grow  the  separate  species  on  separate 
beds  some  feet  apart. 

The  second  main  branch  of  the /a<?T7'/<9/k7- family  arose, 
as  I  have  already  said,  from  the  seeds  of  the  smooth- 
leaved  plants  of  1888.^  It  began  with  two  robust  annual 
smooth-leaved  plants.  Next  year  I  sowed  their  seeds 
on  a  small  bed  on  which  there  flowered  that  summer 

^  See  the  table  on  page  273. 


276  The  Pedigree  Families. 

eight   absolutely   smooth-leaved   individuals   whose   seed 
I  harvested  in  autumn.     There  were  no  mutants. 

In  the  following  year  (1890)  I  sowed  the  seed  in 
a  bed  of  about  3  square  meters,  and  in  the  summer  pulled 
up  all  the  biennial  plants  as  well  as  the  younger  ones  of 
those  tliat  had  produced  a  stem  and  those  whose  leaves 
were  more  or  less  crumpled.  There  were  left,  in  Sep- 
tember, 25  smooth-leaved  individuals  which  however 
flowered  late  and  set  comparatively  little  seed.  Still,  I 
got  about  25  ccm,  of  seed  from  them  and  was  able  there- 
fore to  continue  the  experiment  in  1891  on  a  more  ex- 
tensive scale.  It  occupied,  in  fact,  14  square  meters  and 
mutants  appeared  again.  There  were  two  examples  of 
lata,  an  annual  one  and  a  rosette,  two  feeble  rosettes  of 
cUiptica  and  another  eUiptica  which  was  so  delicate  that 
though  it  developed  a  stem,  it  soon  died. 

From  this  time  I  ceased  to  pay  attention  to  the  special 
peculiarity  of  this  family,  i.  e.,  its  smooth  leaves,  and 
used  it  for  other  purposes.  The  smoothness  of  the 
leaves  however  maintained  itself  (in  spite  of  the  fact 
that  the  plants  were  left  exposed  to  the  visits  of  insects) 
in  the  majority  of  the  plants,  the  remainder  being  ordi- 
nary Lamarckiana.  The  experiments  in  question  were 
discontinued  in  1894,  since  when  I  have  again  got  the 
family  to  breed  true  by  employing  artificial  fertilization. 
But  it  did  not  mutate  any  more  after  that. 

The  experiments  referred  to  above  were  three  in 
number  and  will  be  briefly  described  here :  I  shall  have  to 
deal  with  two  of  them  in  greater  detail  later  on.  The 
object  of  the  first  was  to  breed  a  tricotylous  race.  This 
object  was  attained,  although  the  first  two  generations 
were  not  so  rich  in  tricotylous  specimens  as  were  those 
of  the   similar  experiment  referred  to  above,   with   O. 


The  Laevifolia-Family.  277 

rubrinervis.  But  as  I  had  not  intended  to  go  on  with 
more  than  one  of  these  two  races  I  discontinued  the  ex- 
periment with  this  branch  of  the  family  after  I  had 
recorded  the  1893  crop. 

The  object  of  the  other  two  experiments  was  to 
breed  a  race  with  long  fruits  and  one  with  short  ones 
in  order  to  find  out  the  way  in  which  this  character  re- 
sponded to  cumulative  selection.  (See  Part  III.)  The 
long-fruited  race  gave  rise  to  no  mutants  from  1892  to 
1894  inclusive;  the  short-fruited  race  was,  on  the  other 
hand,  considering  the  relatively  small  extent  of  the  ex- 
periment, extending,  as  it  did,  over  from  4  to  6  square 
meters  each  year,  fairly  rich  in  mutants  (see  page  273). 
It  gave  rise,  in  1893,  to  a  beautiful  rosette  of  eUiptica 
and  two  dwarfs  (an  annual  one  and  a  biennial  one); 
and,  in  1894,  to  two  annual  latas  which  however  had  not 
succeeded  in  flowering  by  the  middle  of  September ;  two 
nibrinerz'is,^  a  rosette  and  a  weakly  stem  which  did  not 
flower;  and,  lastly,  a  rosette  of  elliptica  which  I  did  not 
succeed  in  wintering. 

In  conclusion  I  will  remark  that  the  tricotylous  and 
long-fruited  races  referred  to  are  excluded  from  the  table 
on  page  273,  whereas  the  short-fruited  race  (1892-1894) 
forms  the  direct  line  of  descent  of  the  laevifolia- family . 

In  this  family,  therefore,  there  have  appeared  41 
mutations  altogether,  13  in  the  main  line  of  descent,  21 
from  Lamar ckianas  and  7  from  examples  of  rnhrincrvis. 
This  evening-primrose  experiment  occupied  a  relatively 
wide  area  in  1889  so  that  the  characters  of  the  young 
plants  had  more  chance  of  developing  than  in  previous 
years;  this  circumstance  may,  in  part,  account  for  the 
greater  number  of  mutants  that  appeared  that  year.  This 

*  See  the  table  on  page  273. 


278  The  Pedigree  Families. 

family  originated  from  the  seed  collected  near  Hilversum 
in  1887.  Since  1894  O.  laevifolia  has  always  been  arti- 
ficially self-fertilized,  and  since  that  date  it  has  ceased  to 
mutate. 

§   /.     TWO    LATA-FAMILIES. 

Oenothera  lata  is  one  of  that  group  of  my  new  spe- 
cies which  have  arisen  most  abundantly  from  O.  La- 
marckiana.  It  is  also  the  oldest,  appearing,  as  it  did, 
as  early  as  1887  in  my  garden  from  the  seeds  gathered 
near  Hilversum.  In  the  following  year  it  also  arose  from 
the  seeds  of  the  biennial  plants  which  are  mentioned  in 
§  1  on  page  220  as  forming  the  first  generation  of  my 
chief  experiment. 

From  these  two  mutations  I  have  derived  two  sep- 
arate families,  one  of  which  I  cultivated  till  1890,  whilst 
the  other  has  with  occasional  interruptions  been  con- 
tinued to  the  present  day   (1900). 

Oenothera  lata  is,  as  has  been  already  stated,  solely 
female.  If  it  is  to  bear  seed  it  must  be  fertilized  bv 
other  species.  I  fertilized  it  in  1887  with  the  pollen  of 
Lamarckianas  arising  from  the  same  sample  of  seed. 
From  this  cross  I  got  in  the  following  year  some  latas  and 
some  Lamarckianas,  the  former  in  the  proportion  of  from 
15  to  20  %.i  From  that  time  until  1894  I  had  the  two 
forms  growing  together  and  left  them  to  be  fertilized  by 
insects ;  since  then  I  have  enclosed  the  flowers  of  lata 
in  parchment  bags  and  fertilized  them  myself.  The 
pollen  I  have  used  has  either  been  from  Lamarckiana 
with  the  same  mothers  as  the  latas  in  question,  or  from 
Lamarckianas  of  other  ancestry. 

^  Ueber   erhiingleiche    Kreuzun^en,   Ber.    d.    d.    Bot.    Ges..    Nov. 
1900,  Bd.  XVTII,  p.  435. 


Two  Lata-Faniilies.  279 

I  made  the  most  extensive  sowing,  in  these  famihes, 
and  the  richest  in  mutations,  in  1900;  I  shah  deal  with  it 
first.  In  August  1899  I  artificially  fertilized  18  plants 
of  O.  lata  in  parchment  bags,  all  with  pollen  of  0.  La- 
marckiana  which  had  either  grown  from  /a/a-seed  or 
were  from  pure  race.  In  the  spring  of  1900  I  sowed 
the  seed,  of  each  plant  separately,  in  pans^  and  ])ricked 
out  all  the  young  seedlings,  irrespective  of  their  char- 
acters, into  wooden  boxes  filled  with  manured  soil  This 
was  done  as  soon  as  the  first  leaves  had  completely  un- 
folded and  before  the  characters  of  any  mutants  that 
there  might  be  were  discernible.  The  seedlings  remained 
in  the  wooden  boxes  until  they  had  become  strong  young 
rosettes ;  and  it  was  in  these  boxes  that  the  mutants  could 
first  be  recognized.  Plate  IV  and  figure  48  give  an  idea 
of  the  appearance  of  the  boxes  at  this  stage. 

Plate  IV  is  reproduced  from  a  photograph  which  I 
took  on  the  18th  of  May  1900.  The  camera  was  so 
placed  that  its  optical  axis  was  vertical ;  all  that  then 
remained  to  be  done  was  to  push  the  box  under  the  cam- 
era at  the  proper  distance  from  it. 

This  plan  obviated  the  necessity  of  tilting  the  box 
which  might  easily  have  fatal  results  for  the  young 
plants ;  and  made  it  possible  to  grow  them  subsequently. 

I  dealt  with  over  2000  seedlings  in  this  experiment. 
So  that  there  was  great  opportunity  for  choosing  good 
groups  for  photographing.  I  either  chose  groups  in- 
cluding many  examples  of  mutants  of  the  same  species 
(Plate  IV)  or  groups  comprising  many  different  kinds  of 
mutants  (Fig.  48).     I  mention  this  because  the  figures 

*My  plan  was  to  sterilize  the  soil  in  these  pans  by  heating  it. 
before  sowing  the  seed,  up  to  90-100°  C.  This  killed  the  seeds  of 
weeds  which  the  soil  invariably  contained.  The  soil  was  not  man- 
ured.    My  seedlings  did  splendidly  in  soil  sterilized  in  this  way. 


280 


The  Pedigree  Families. 


might  give  the  impression  that  mutants  are  much  more 
numerous  than  they  really  are.  In  this  culture  there 
were  as  a  matter  of  fact  60  mutants  among  2070  seed- 
lings; that  is — about  3  %.  If  I  had  wanted  to  show  this 
proportion  in  the  photographs  each  one  could  not  have 
shown  more  than  one  mutation  at  the  most.  But  the  mu- 
tants are  very  irregularly  scattered  amongst  the  other 


Fig.  48.    Mutation  in  the  /a?a-family    (1900).     Origin  of  O. 

albida,  O.  oblouga,  O.  ruhrinervis  and  0.  subovata.  The  plants 

are  arranged  in  3  rows  as  follows : 
Upper  row:    Lam.     Lam.  lata         Lam.  ruhrinervis 

Second  row:  lata       albida  albida     lata  Lam. 

Third  row:     Lam.     subovata     albida     oblonga     Lam. 

seedlings  and  I  naturally  chose  groups  in  which  there 
happened  to  be  a  lot  of  them.  The  most  abundant  mu- 
tation in  this  experiment  as  in  others  was  0.  alhida. 
On  Plate  IV  three  are  to  be  seen :  the  third  plant  in  the 
upper  row  is  one ;  another  is  the  second  plant  in  the 
third  row;  another  the  first  plant   (on  the  left)   in  the 


Two  Lata-Families.  281 

fourth   row.      The   plants   are   transplanted   in    rows   in 
order  to  make  the  best  advantage  of  the  availal)le  space. 

It  should  be  observed  that  the  pedigree  of  this  culture 
contains  seven  successive  generations  of  lata,  the  first  of 
which  arose  from  a  Lamarckiana  which  I  jj^rcw  in  my 
garden.  This  group  arose  from  a  single  [)lant  which 
was  fertilized  with  the  pollen  of  a  plant  of  Lamarck's 
Evening  Primrose  of  similar  parentage.  The  origin  of 
this  race  vv'as  therefore  as  pure  as  the  unisexual ity  of 
lata  permitted. 

Seedlings  of  O.  alhida  are  very  easy  to  recognize. 
Nothing  short  of  seeing  the  plants  themselves  can  really 
give  an  accurate  idea  of  these  phenomena :  but  the  pic- 
tures may  serve  to  convey  the  impression  of  the  ])rocess 
of  mutation.  The  plate  shows  besides  O.  alhida,  five 
plants  of  O.  lata  and  six  of  O.  Lamarckiana.  The  for- 
mer can  be  recognized  by  their  bright  green  round  leaves, 
the  latter  by  their  darker  green  leaves  which  are  more 
or  less  pointed.  The  three  O.  alhida  are  much  smaller, 
of  a  paler  color,  and  with  narrower  leaves. 

The  plate  shows  another  case  besides  these.  I  mean 
the  plant  at  the  right-hand  end  of  the  second  row.  It 
has  narrow  leaves  and  does  not  look  quite  like  any  of  the 
tvpes  hitherto  recognized  in  these  experiments.  Does 
it  represent  a  new  form?  I  devoted  every  possible  care 
to  its  further  cultivation:  but  it  sickened  and  died  before 
its  mature  characters  had  developed.  The  three  alhidas 
also  got  no  further  than  the  rosette  stage. 

Another  group  from  the  same  experiment  is  faith- 
fully represented  by  photography  in  Fig.  48.  The  group 
was  taken  in  the  way  described  above  on  the  25th  of 
May;  it  arose  from  another  parent  plant,  of  the  same 
experiment  of  1899,  which  had  likewise  been   fertilized 


282 


The  Pedigree  Families. 


with  the  pollen  of  a  closely  related  individual  of  0.  La- 
mar ckiana.  There  happened,  in  this  group,  to  be  four 
mutations  so  close  to  each  other  that  they  could  all  be 
photographed  together:  they  did  not  occupy  a  space  of 


4 


Fig.  49.  Oenothera  rubrinervis.    A  mutated  specimen.    It  is 
the  same  plant  we  have  seen  in  the  right  upper  corner  of 
Fig.  48,  but  now  in  flower.  It  originated  from  six  genera- 
tions of  O.  lata  which  in  their  turn  arose  from  O.  La- 
marckiana. 

more  than  13  X  18  centimeters  so  that  I  could  photo- 
graph them,  natural  size,  on  a  plate  of  these  dimensions. 


Two  Lata-Families.  283 

The  mutations  depicted  were  O.  ohlonga,  0.  riibri- 
ncrvis,  O.  siihovata,  of  each  of  which  there  was  one  ex- 
ample, and  0.  albida,  of  which  there  were  three.  Besides 
these  six  0.  Lamarckiana  and  three  O.  lata  can  be  seen. 
The  three  alhidas  are  easily  recognized;  they  are  Nos. 
2  and  3  in  the  middle  row  and  No.  3  in  the  lower.  0. 
nihrinervis  will  be  seen  at  the  right  of  the  upper  row, 
easily  recognizable  by  its  narrow  leaves ;  0.  siibovafa 
and  0.  ohlonga  are  Nos.  2  and  4  in  the  lower  row\ 

These  two  were  hardly  old  enough  to  be  identified 
on  the  day  they  were  photographed—  especially  the  siih- 
ovata. 

Of  the  plants  shown  in  Fig.  48  I  kept  one  O.  lata  and 
all  the  mutants,  planting  them  out  on  a  special  bed.  The 
O.  lata  and  0.  nihrinervis  produced  stems  and  flowered 
in  August,  the  rest  behaved  as  biennials  and  remained  in 
the  rosette  stage.  When  the  example  of  0.  rubrincrvis 
flowered,  and  the  characters  of  this  species  were  devel- 
oped to  their  full  extent,  I  pulled  it  up  and  photographed 
it  (Fig.  49)  ;  it  was  a  very  beautiful  example  of  the  rule 
that  new  species  not  only  arise  suddenly  and  without 
transitional  stages  from  the  parent  species  but  with  all 
their  characters  fully  developed. 

Of  the  alhidas  two  died  during  the  course  of  the 
summer,  whilst  the  third  together  with  the  O.  ohlonga 
2:rew  well  into  the  autumn.  The  0.  snhovata  was  much 
damaged  by  the  ravages  of  insects  but  managed  to  re- 
main alive. 

Another  O.  ohlonga,  which  arose  by  mutation  in  the 
same  experiment,  developed  a  stem  and  flowered  in 
August.  Fig.  50  is  a  picture  of  it.  It  arose  from  the 
seeds   of  the   same  mother  as  the   culture   depicted   in 


284 


The  Pedigree  Families. 


Plate  IV  and  grew  in  the  same  box  quite  close  to  the 
group  that  was  photographed. 

The  1900  crop  contained,  besides  the  mutants  figured, 

a  great  many  others  partly 
of  the  same  species  and 
partly  of  others.  The  lat- 
ter were  three  O.  fianella, 
one  O.  elliptic  a  and  one 
O.  sublinearis.  This  lat- 
ter, which  is  one  of  my 
rarest  species,  I  photo- 
graphed, like  the  others 
referred  to  above,  whilst 
it  was  flowering  in  xA.u- 
gust.  I  shall  give  the  fig- 
ure of  it  when  I  come  to 
describe  the  species  later 
on  (see  Fig.  85). 

In     previous     genera- 
tions this  family  was  very 
poor  in  mutations,  for  the 
simple  reason  that  it  was 
cultivated  on  a  small  scale. 
One    year    (1898)    there 
arose  in  it,   one  example 
of  0.  scintillans  and  an- 
other year  an  entirely  new 
form   0.   semilata.     This 
looks  very  much  like   0. 
lata  but  is  much  more  ro- 
bust and  bears  plenty  of  pollen.     It  is  one  of  my  rarest 
new  species,  arising,  as  it  did.  only  twice  altogether. 
On  page  285  I  give  the  genealogy  of  this  whole  fam- 


Fig.  50.  Oenothera  ohlonga.  An  ex- 
ample which  arose  by  mutation 
from  the  same  parentage  as  the 
plant  shown  in  Fig.  49. 


Two  Lata- Families. 


285 


ily.  Its  origin  is  the  same  as  lliat  of  the  main  h"ne  of 
descent  of  the  Lamarckiana-i^xnWy  referred  to  on  page 
224.  The  seeds  of  the  nine  biennai  individuals  of  the 
period  18S6-7,  there  mentioned,  gave  ten  mutants:  five 


OENOTHERA  LAMARCKIANA. 

C 

PEDIGREE  OF  THE  FIRST  LATA-FAMILY. 

(The  figures  refer  to  the  number  of  seedlings;  the  sign 
that  this  number  was  not  counted.) 


means 


GENER.\TIONS 


SPECIES 


albida 


na- 
nella 


O.  lata  I 

+    ! 

O.Lam. 


ob- 
Jongra 


rubrr- 
nervis 


sub- 
line- 
aris 


ellip-       sub- 
tica       ovata 


VIII 


VII 


VI 


V 


IV 


III 


II 


8th  gen. 
1900 

7th  gen. 
1899 

6th  gen 
1898 

5th  gen. 
1897 

4th  gen. 
1895 

3rd  gen. 
1894 

2nd  gen. 

(biennial) 
1888  1889 

1st  gen. 
(biennial) 
1886-1887 


Lam. 


dwarfs  and  five  O.  lata ;  it  is  from  these  latter  that  the 
family  in  question  arose.  But  in  most  years,  as  I  have 
already  stated,  they  did  not  mutate. 


286  The  Pedigree  Families. 

Let  us  now  turn  to  the  description  of  the  second  lata- 
family.  This  arose  in  my  garden  in  1887  from  seeds 
which  I  took,  in  the  preceding  autumn,  from  a  quinque- 
locular  fruit  of  an  otherwise  normal  plant  of  Lamarckiana 
growing  in  the  field  at  Hilversum.  Of  these  seeds  not 
many  germinated  and,  of  the  plants  which  arose  from 
those  which  did,  only  five  flowered  in  the  first  year  in 
my  garden ;  the  rest  were  pulled  up  and  thrown  away. 
Of  these  five,  two  were  0.  lata  and  three  O.  Lamarckiana. 
The  seed  of  the  two  former  was  harvested  separately 
and  sown  in  the  following  spring  (1888)  for  the  con- 
tinuation of  the  experiment. 

In  1887  no  other  Oenotheras  flowered  in  my  experi- 
mental garden  besides  the  five  individuals  mentioned 
above.  The  Lanwrckiajta-iamily  was  flowering  at  that 
time  in  the  Botanical  Garden  in  a  bed  about  150  meters 
from  my  garden  and  separated  from  it  by  shrubbery. 
From  the  seeds  of  the  two  original  lata  plants  there  arose 
in  April  and  May  1888,  614  individuals  of  which  21  % 
exhibited  the  lata  characters.  Towards  the  end  of  the 
summer  I  found  that  about  one-third  of  the  plants  had 
remained  in  the  rosette  stage  whilst  two-thirds  had  de- 
veloped stems.  Lamarckiana  and  lata  behave  very  much 
alike  in  this  respect. 

Of  the  annual  I  at  as,  which  could  be  fertilized  by  the 
rest  of  the  plants  up  till  the  middle  of  September,  I  saved 
the  best  39  •  whilst  all  the  rest  with  a  single  exception 
I  pulled  up  and  threw  away. 

This  exception  was  an  example  of  0.  scintillans,  the 
first  that  occurred  in  my  experiments.  Its  mother  is 
therefore  one  of  the  latas  of  1887,  its  father  one  of 
the  three  Lamarckianas  of  the  same  family.  This  scin- 
tillans  was   biennial,    flowering   and    ripening   its    fruits 


Two  Lata-Families.  287 

in  1889.  Its  seeds,  some  of  which  were  sown  in  1890 
and  some  in  1894,  gave  rise  for  the  most  part  to  the 
same  form.  The  cuhure  of  1890  consisted  partly  of 
annual  plants  (10  of  which  w^ere  scintillans)  and  partly 
of  biennial  ones  (comprising  26  scmtillans) ,  the  former 
flowered  well  but  too  late;  the  others  were  frozen  in  the 
winter,  so  that  I  got  no  seed  from  this  experiment.  The 
1894  crop  w^as  entirely  biennial  and  contained  11  plants 
of  scintillans  which  set  seed  in  1895. 

Let  us  now  return  to  the  main  line  of  descent  of  our 
family.  On  the  18th  of  April  1889  I  sowed  the  seed 
which  had  been  harvested,  on  a  bed  (about  3  square 
meters  in  size)  which  was  fairly  thickly  covered  with 
plants  towards  the  end  of  May  when  the  latas  could  easily 
be  distinguished  from  the  Lainarkiauas.  Most  of  the 
latter  were  removed.  Towards  the  end  of  July,  12  annual 
specimens  of  lata  flowered :  the  rest  of  the  latas,  which 
had  either  developed  stems  too  late  or  still  remained  in 
the  rosette  stage,  were  weeded  out.  Of  those  that  flow- 
ered eleven  set  seed,  and  were  harvested  together. 

Part  of  the  seed  was  sown  in  the  following  year : 
a  smaller  sample  was  kept  till  1894,  in  which  year  they 
gave  rise  to  340  seedlings  of  which  52  were  lata :  these 
were  however  not  cultivated  further. 

I  sowed  the  seed  to  produce  the  fourth  generation 
on  the  5th  of  May  1890;  as  before,  on  a  bed  of  about 
3  square  meters.  At  the  beginning  of  Jnly  there  were 
on  this  bed  79  specimens  of  lata  and  many  of  La- 
marckiana.  The  former  were  partly  annual,  partly  bi- 
ennial. The  annual  plants  did  not  flower  before  the 
middle  of  September  and  only  six  latas  set  seed  which 
ripened  very  late  and  could  not  be  harvested  before  De- 
cember. 


288 


The  Pedigree  Families. 


The  1890  crop  contained,  1)esides  the  two  parent 
types,  three  mutations,  viz.,  one  elliptica  and  two  spathit- 
lata  which  however  did  not  flower  and  were  not  cultivated 
further. 

Mention  must  here  be  made  of  a  Lainarckiana  in  the 
1889  crop,  in  some  of  the  flowers  of  which  the  tips  of 
the  sepals  had  become  broad  and  the  sepals  themselves 


OENOTHERA  LAMARCKIANA. 

D 

PEDIGREE  OF  THE   SECOND  LATA-FAMILY. 
(The  fip^ures  refer  to  the  numbers  of  seedlings.) 


SPECIES 

GiiA  nn  A  nurs  5 

elliptica 

Lamarck- 
iana 

I        lata        i  spathulata     elliptica 

1                      1 

V 

5th  generation 
1890 

4th  generation 
1889 

3rd  generation 
1888 

1 

2nd  generation! 
1887 

1st    generation 

Hilversum 

1886 

1 

1 

Lam. 

3  lata      lata 

2                1 

IV 

^_ 

Lam. 

lata 

III 

Lara. 

lata 

1  scintillans 

II 

3  Lam. 

V 

2  lata 

I 

La] 

m. 

leaf-like.  I  sowed  the  seeds  of  this  plant,  but  tlie  a])- 
normality  was  not  repeated :  there  were  however  among 
its  offspring  3  latas  and  one  elliptica.  The  experiment 
was  not  continued. 

For  the  next  three  years  (1891-3)  I  did  not  culti- 
vate either  this  or  the  other  lafa-fm-nilyl  on  account  of 
the  difficulties  of   fertilization.      In    1894  I   took  it  up 


Mutations  in  Other  Families.  289 

again  and  sowed  the  1890  seed.  It  gave  20  examples  of 
O.  Lamarckiana  and  6  of  lata — only  26  seedlings  alto- 
gether. The  6  latas  were  annual,  flowered  well,  and 
provided  material  for  an  investigation,  to  be  referred 
to  later,  into  the  sterility  of  the  pollen. 

The  foregoing  account  can  be  summarized  in  tlie 
table  on  page  288. 

The  question  naturally  arises  whether  the  mutability 
in  this  family  comes  from  the  father  or  from  the  mother. 
I  believe  from  the  father  because  my  new  species  have  as 
a  rule  bred  true  and  at  any  rate  have  mutated  much  less 
than  Lamarckiana  itself.  On  the  other  hand  it  seems 
probable  that  crossing  in  itself  favors  the  production  of 
mutations. 


§  8.    MUTATIONS  IN  OTHER  FAMILIES. 

Mutations  have  also  occurred  repeatedly  in  cultures  of 
O.  Lamarckiana,  which  have  not  yet  been  described.  It 
may  almost  be  said  that  every  extensive  sowing  will  give 
mutations ;  provided  that  the  plants  are  not  grown  so 
thickly  that  the  majority  of  them  are  prevented  even  from 
showing  their  characters ;  and  provided  that  the  beds  are 
carefully  examined.  For  before  a  plant  begins  to  develop 
a  stem  it  forms  a  rosette  with  a  radius  of  some  20  to  30 
centimeters,  and  there  is  not  room  for  many  flowering 
examples  on  a  bed — 20-40  at  the  most  per  square  meter. 

My  mutations  were  almost  always,  at  any  rate  in 
their  yoimg  stages,  more  delicate  than  the  parent  species 
so  that  they  were  very  liable  to  be  crowded  out. 

I  propose,  therefore,  now  to  say  something  about  the 
methods  of  cultivation,  and  about  the  search  for  muta- 


290  The  Pedigree  Fain  Hies. 

tions  with   especial   reference  to  the  characters   of  the 
young  plants. 

I  shall  describe  these  characters  in  greater  detail  in 
the  following  chapter,  but  it  seems  desirable  to  preface 
it  by  a  short  comparative  resume. 

I  began  by  sowing  the  seed  in  the  garden.  The 
result  of  that  was,  as  I  have  already  mentioned,  that  part 
of  the  seed  remained  in  the  ground  and  germinated  in 
subsequent  years.  So  that  each  particular  part  of  the 
garden  could  only  be  used  once.  I  therefore  adopted 
the  plan  of  sowing  the  seed  in  pans ;  the  soil  for  them  was 
bought  from  a  nursery  and  was  sterilized  so  that  any 
seeds  of  Oenothera  that  happened  to  be  in  it  were  des- 
troyed— a  fact  completely  proved  by  numerous  control 
experiments.  The  seedlings  remained  in  these  pans  when 
ever  possible,  until  they  were  old  enough  to  be  identified, 
and  until  the  different  kinds  had  been  recorded ;  if  this 
was  not  possible  they  were  transplanted  into  wooden 
boxes  measuring  30  by  50  centimeters  and  10  centimeters 
deep.  They  remained  in  these  until  they  could  be  planted 
out  in  the  beds. 

The  plants  were  only  grown  in  pots  when  it  was 
desirable  that  they  should  be  treated  particularly  care- 
fully or  when  especially  robust  plants  were  wanted. 

A  sharp  distinction  is  to  be  drawn  between  crops 
which  are  intended  to  flower  and  such  as  are  recorded 
and  thrown  away  before  the  plants  develop  stems.  The 
former  are  almost  always  transplanted  from  the  pans 
before  the  characters  of  the  new  species  are  recognizable ; 
the  latter  are  very  often  kept  in  the  pans  until  they  are 
done  with. 

Some  forms  are  recognizable  as  soon  as  the  hrst 
leaves  are  developed.     This  is  almost  always  true  of  0. 


Mutations  in  Other  Families. 


291 


lata  and  very  often,  especially  if  the  seeds  are  not  sown 
too  thick,  of  O.  nanella.  0.  albida  can  also  be  recognized 
very  early.  0.  oblong  a  and  O.  rubrinervis  often  cannot 
be  identified  until  much  later :  and  0.  scintillans  later 
still.  In  fact  it  was  quite  an  exception  when  I  recognized 
one  of  the  last  named  in  the  pans  at  all  with  sufficient 
certainty :  when  they  were  being  transplanted  they  were, 
commonly,  simply  taken  for  weak  plants. 


Fig.  51.  A  mutation  in  a  seed-pan.  The  plant  in  the  middle  is 
an  O.  lata  mutant.  Tlie  whole  culture  arose  from  a  cross  be- 
tween O.  Lamarckiana  and  O  uaneUa.  to  which  two  types  all 
the  rest  of  the  plants  in  this  figure  belong. 


The  superficial  area  of  soil  contained  in  these  pans 
is  25  X  25  centimeters.  From  %  to  %  cubic  centimeters 
of  seed  is  sown  in  them.  Under  these  conditions  the 
plants  have  ample  room  when  they  are  young.  But  if 
they  grow  to  an  age  at  which  the  mutants  amongst  them 
are  recognizable  they  become  much  too  thick  for  it  to  be 


292  The  Pedigree  Fauiilies. 

possible  to  photograph  them.     This  can  only  be  done 
when  few  seeds  are  sown,  or  when  few  germinate. 

Fig.  51  shows  an  example  of  such  a  case.  The  seeds 
sown  were  the  result  of  a  cross.  O.  Lamarckiana  was 
crossed  with  O.  nanel.a  in  August  1899;  about  250  of  the 
seeds  germinated  and  about  30  %  of  the  plants  they  gave 
rise  to  were  0.  nanella.  It  is  easy  to  distinguish,  in  the 
figure,  between  the  loose  rosettes  of  the  parent  species 
and  the  rosettes  of  the  dwarf  by  the  fact  that  in  the 
latter  the  central  leaves  are  more  closely  packed.  Right 
in  the  middle  there  stands  rather  alone  one  O.  lata  easily 
recognizable  by  its  round  (as  opposed  to  pointed)  leaves. 
It  was  rather  covered  by  its  neighbors,  so  before  photo- 
graphing it  I  put  its  leaves  over  those  which  were  cov- 
ering it.  Otherwise  nothing  in  the  group  was  interfered 
with. 

The  two  parents  crossed  were  of  pure  origin ;  the 
Lamarckiana  came  from  the  main  line  of  descent  of  my 
experiment  (after  eight  generations  of  cultivation)  the 
nanella  arose  from  this  Lamarckiana  race  in  1895  and 
had  since  bred  true  for  five  generations.  The  lata  in 
Fig.  51,  therefore,  had  no  ancestors  of  a  like  character 
at  any  rate  during  this  period  (1886-1899).  In  the 
lateral  branches  of  this  pedigree  however,  this  form  has 
arisen  almost  every  year. 

The  characters  of  the  young  plants  can  be  most  clearly 
apprehended  for  the  purposes  of  identification,  from  the 
figures  of  the  rosettes  which  wiM  be  given  later.  Mean- 
while I  propose  to  describe  here  the  typical  form  of  the 
adult  leaves  of  the  rosettes  of  the  various  forms  (Figs. 
52  and  53).  The  leaves  are  photographed  one-half  the 
natural  size  and  were  taken  from  the  plants  in  the 
wooden  boxes  at  the  beginning  of  June.     The  cultures 


Mutations  in  Other  Families. 


293 


were  pure,  that  is  to  say  each  species  in  each  culture  was 
raised  from  seeds  of  that  species :  this  made  it  easy  to 
choose  a  good  average  form  of  leaf. 

The  most  easy  to  recognize  are  O.  nancUa  (Fig.  52n) 
and  0.  lata  (Fig.  52/).  The  former  has  rather  short- 
stalked  slightly  undulating  leaves  with  hroad  ]:)ases;  the 
result  being  that  the  leaves  have  the  appearance  of  being 


Fig.  52.  Fully  grown  leaves  of  young  rosettes  in  June.  L, 
Oenothera  Lamarckiana ;  n.  O.  nanella;  g,  O.  gigas;  r, 
O,  rubrinervis ;  I,  O.  lata;  s,  O.  scintillans. 


much  crowded  in  the  heart  of  the  rosette.  The  latter 
has  long-stalked  leaves  whose  apices  are  quite  round. 
Their  surface  is  very  uneven  but  their  margin  is  fairly 
level  and  tears  very  easily  if  one  attempts  to  press  the 
leaf  flat  (hence  the  small  tear  at  the  tip).     O.  gigas  is 


294  The  Pedigree  Families. 

distinguished  from  0.  Lamarckiana  by  its  much  more 
robust  and  still  broader  leaves  (Fig.  d2  g  and  L).  0. 
nibrinervis  (Fig.  52  r)  and  0.  scintillans  (s)  have  nar- 
rower leaves,  those  of  the  former  being  gray-green,  those 
of  the  latter  dark  green,  whereas  the  surfaces  of  the 
leaves  of 'both  these  forms  are  hardly  crumpled  at  all. 
O.  albida  (Fig.  53  a)  and  0.  oblonga  (o)  are  scarcely 
recognizable  at  this  age  by  the  form  of  their  leaf.  O. 
albida  varies  very  much  according  as  whether  one  is 
dealing  with  the  ordinary  w^eakly  forms  or  with  plants 
which  have  grown  up  strong  as  a  result  of  special  care. 

fThe  leaves  of  the  former  are 
small  and  narrow,  pale  green  and 
often  even  almost  white ;  those 
of  the  latter  are  chiefly  recog- 
nizable by  their  pale  color.  O. 
oblonga  has  leaves  with  very 
broad  main  veins :  this  breadth 
is   much   more   striking   on   the 

Fig.  53.  Full  grown  leaves  "PP^r  than  on  the  lower  surface 
of  young  roseues  in  June,  which  is  the  one  figured.  They 
a,  O.  albida;  o,  O.  oblonga.  •         i         i        ,  i         i 

are  pomted  and,  when  the  plants 

are  young,  broad ;  but  later  they  become  very  narrow. 

For  comparison  with  the  leaves  of  the  young  plants 

there  are  shown  in  Fig.  54  the  grown  leaves  of  flowering 

plants.     The  leaves  were  plucked  from  the  plants  just 

below  the  first  flower-bearing  nodes.    They  are  the  same 

species  as  those  whose  seedling  leaves  have  already  been 

figured,  with  the  exception  of  O.  lata,  O.  Lamarckiana 

and  O.  nanella.^ 

^  I  have  copied  these  leaves  photographically  by  spreading  slightly 
faded  ones  out  on  sensitized  paper  and  then  printing  under  glass  ni 
an  ordinary  printing  frame.  I  then  photographed  the  prints,  reducing 
them  to  about  one-half. 


Mutations  ui  Other  faniilies. 


295 


The  leaves  of  O.  gigas  are  recognizable  by  their 
greater  breadth ;  all  of  the  others  that  are  figured  are 
narrower  than  0.  Lamarckiana.    The  leaf  of  0.  oblunga 


Fig.  54.  Leaves  from  the  stems  of  flowering  plants  of 
g,  O.  gigas;  r,  O.  rubrinervis ;  o,  O.  oblonga;  a,  O.  albida; 
s,  O.  scintillans. 


is  characterized  by  its  broad  median  vein ;  that  of   O 
rnbrinerz'is  is  slightly  more  pointed  than  gigas  and  ob- 
longa ;  moreover  its  surface  is  usually  \cr\-  uneven.    But, 


296  The  Pedigree  Faniilics. 

the  leaves  of  these  three  types,  ohlonga,  alhida  and  sc'in- 
tillans,  can  really  only  be  distinguished  by  their  color 
and  substance. 

The  various  new  species  (with  the  single  exception 
of  O.  Icptocarpa  which  is  not  recognizable  until  it  flow- 
ers) can,  however,  be  recognized  with  certainty  at  any 
stage  in  their  development  by  their  leaves.  All  the  later 
characters,  the  form  of  the  flowering  branches  and  of 
the  flowers  themselves,  in  0.  lata  the  absence  of  pollen, 
the  size  of  the  fruits  and  the  abundance  of  seed — can 
be  predicted  from  the  leaves,  if  the  species  in  question 
lias  once  been  seen  in  flower  and  fruit.  But,  as  a  matter 
of  fact,  I  have  planted  out  every  year,  for  further  growth, 
a  greater  or  smaller  number  of  the  plants  which  had  been 
sorted  by  their  seedling  characters;  and  in  no  case  has 
my  identification  proved  to  be  erroneous. 

I  have  sought  for  mutants  among  the  crops  from 
Oenothera  seeds  as  often  as  possible  by  this  method. 
Whether,  and  in  what  quantities,  they  appear  depends  in 
great  measure,  as  I  have  already  said,  on  the  extensive- 
ness  of  the  sowing.  But  these  things  are  undoubtedly 
influenced  by  other  causes  operating  during  germination 
(see  p.  263)  or  fertilization  or  even  earlier. 

As  a  rule  the  new  species  proved  much  less  mutable 
than  the  original  O.  Lainarckiana  from  which  they  orig- 
inated. It  is  only  the  inconstant  forms  amongst  them 
which  exhibit  a  very  high  degree  of  mutability,  as  for 
example  O.  scintillans. 

The  power  to  mutate  is  maintained  after  crossing 
and  in  cases  where  the  original  form  O.  Lamarckiana 
reappears  out  of  a  cross  it  does  so  with  its  full — I  had 
almost  said  normal — capacity  for  mutation. 


Mutations  in  Other  Fauiilies. 


297 


One  of  two  instances  will  serve  to  exemplify  these 
generalizations  here.  I  shall  reserve  a  more  complete 
proof  of  them  until  I  come  to  the  description  of  the 
separate  new  species. 

Pure  sowings  of  0.  Icptocarpa,  O.  nancUa  and  0.  oh- 
longa  gave  rise  solely  to  their  own  type  with  the  excep- 
tion of  the  following  mutants.  Subjoined  is  a  list  of 
these,  together  with  the  date  of  the  experiment  and  the 
number  of  the  seedlings. 


MUTANTS  ARISING   FROM   NEW   SPECIES. 

NUMBER  OF 


SPECIES 

DATE 

SEEDLINGS 

MUTANTS 

o. 

leptocdrpa 

1896 

500 

2  fianel/a 

o. 

nanella 

1897 

760 

1  oblon^a 

o. 

oblonjra 

1897 

2150 

2  albida 
1  elliptica 

Total 

1  rtibrinervis 

3410 

7  mutants 

That  is  to  say  a  proportion  of  about  0.2  %,  whereas  O. 
Lamar ckiana  usually  has  1-3  %  and  often  more  mutants. 

O.  scintillans  is  an  example  of  an  inconstant  new  spe- 
cies in  as  much  as  often  only  about  Ys  of  its  offspring 
are  scintillans  (see  p.  245)  ;  the  two  remaining  thirds 
are  composed  of  partly  0.  ohlonga  and  partly  0.  La- 
marckiana  and,  to  a  much  less  extent,  of  the  two  other 
common  species  0.  lata  and  O.  nanella. 

I  found  the  following  numbers  of  these  in  the  experi- 
ments with  O.  scintillans  in  which  the  seeds  were  set  on 
typical  plants  which  had  been  fertilized  by  their  own 
pollen. 


298 


The  Pedigree  Families. 


MUTANTS  ARISING  FROM  O.  SCINTILLANS. 


DATE 

NUMBER  OF 
SEEDLINGS 

LATA 

NANELLA 

1896 

268 

8 

1 

1897 

572 

3 

3 

1898 

447 

1 

0 

1898 

587 

3 

2 

1899 

148 

2 

0 

1899 

5850 

21 

23 

Totals     7872 

38 

29 

67 

That  is,  rougiily  1  %  or  about  as  mucli  as  in  the  case  of 
O.  Lainarckiana  itself. 

A  parahel  resuk  is  got  with  crossings.  From  these 
there  arise  the  two  parent  forms  and  very  often  O.  La- 
inarckiana itself,  even  when  it  was  not  one  of  the  parents.^ 
But  other  mutations  occur  as  well,  as  the  following  in- 
stances  will   show. 

MUTANTS  ARISING  FROM  THE  CROSS  O.  LAMARCKIANA  X  O. 

NANELLA. 

RUBRI-       ELLIP- 


NUMBER  OF 
DATE  _  ALBIDA 

SEEDLINGS 


LATA       OBLONGA 


NERVIS         TICA 


1897 

1341 

1897 

1051 

1898 

474 

1899 

3815 

1899 

1606 

7 
5 
2 
3 

5 


20 

12 

5 

1 


8283  1  22  38 

Altogether  64  mutants,  or  nearly  1  %. 


'  See  Ber.   d.   d.   Bot.   Gesellschaft,  Bd.   XVIII,   igoo,     Heft   X, 
P-  435- 


Mutations  in  Other  Families. 


299 


MUTANTS  ARISING  FROM  THE  CROSS  O.  LATA  X  O.  NANELLA. 


DATE 

NUMBER  OF 
SEEDLINGS 

ALBIDA 

OBLONGA 

RUBRINE 

1895 

63 

— 

1 

1897 

837 

6 

7 

1898 

101 

1 

1 

1898 

146 

3 

1899 

280 

5 

3 

1900 

159 

3 

1 

1586  15  14 

Altogether,   31   mutants,  or  nearly  2  % 


DATE 

NUMBER  OF 
SEEDLINGS 

MUTANTS 

1896 

30 

2  oblonga 

1900 

80 

1  lata 
1  nanella 

1897 

200 

8  oblonga 
1  elliptica 

1899 

299 

2  nanella 
1  scintillans 

1900 

743 

13  albida 

Totals 

1352 

29  mutants 

MUTANTS   ARISING   FROM    CROSSES   WITH    THE   OLDER 

SPECIES. 

NATURE  OF  CROSS 

O.  Lam.  X  O.  bienfiis 
O.  Lam.  X  O.  biennis 

O.  Lam.  X  O.  suaveolens 

O.  lata  X  O.  biennis 

O.  lata  X  O.  suaveolens 

That  is,  somewhat  over  2  %  of  mutants. 

The  mutability  of  all  these  crosses  is  thus  shown  to 
be  about  the  same  as  that  of  0.  Laniarckiana. 

I  have,  finally,  tested  the  offspring  of  crosses  in  the 
second  generation  If  we  select  the  seed  of  hybrids 
which,  to  judge  by  their  characters,  belong  to  some  one 
of  the  new  species,  we  get,  by  sowing  it,  proportions  of 
mutants  which  closely  correspond  with  those  given  on 
p.  297.  But  if  we  select  the  seed  of  self-fertilized  hybrid 
Lamarckianas  we  find,  on  the  contrary,  that  they  exhibit 
the  same  dee^ree  of  mutabilitv  as  ordinary  ones. 


300  The  Pedigree  Families. 

MUTANTS   ARISING    FROM    PLANTS   OF   LAMARCKIANA 
WHICH   HAVE  THEMSELVES  ARISEN  FROM  CROSSES. 

Experiments  Carried  Out  in  1898. 

oDr»ocT7vTr-  '  T         a    a         NUMBER  OF  MUTANTS  IN  1898 

CROSSINGS  IN  i»9b       SEEDLINGS     a/dtda    lata    nanella    oblonga 


0.  Lam.  X  0.  7ianeUa 

1063 

1 

— 

5 

2 

0.  lata  X  0.  Lam. 

427 

3 

2 

0.  lata  X  0.  nanella 

1693 

1 

1 

12 

1 

•  1       t  (     1 .    1  i         ( t 

390 

1 

6 

1 

0.  lata  X  hrevistylis 

1026 

2 

3 

2 

Totals    4599  2  7  26  8 

That  is,  altog,ether  43,  or  about  1  %  of  mutants. 

We  may  sum  up  by  saying  that  we  never  find  an}^ 
more  than  sHght  deviations  from  the  original  degree  of 
mutabihty  exhibited  by  O.  Lamarckiana.  It  seems  to 
retain  this  property  through  all  generations  and  in  spite 
of  crossing;  at  any  rate  in  the  course  of  my  experiments. 
In  the  new  species,  on  the  contrary,  this  capacity  for 
mutation  is  modified ;  for  it  is  a  constant  feature  of  them 
that  their  mutability  is  much  diminished.  It  has,  how- 
ever, not  completely  disappeared,  and  the  power  of  giving 
rise  to  the  same  new  species  as  does  the  parent  form  has 
been  evidently  transmitted  to  them. 

§  9.    MUTATIONS  IN  NATURE. 

The  object  of  the  experiments  in  my  garden  was  not 
to  induce  mutations,  but  to  make  a  closer  study  of  the 
process  of  mutation  than  was  possible  in  nature. 

Of  course,  I  regard  the  induction  of  mutations  as  a 
much  bigger  problem  the  solution  of  which  I  would 
gladly  have  attempted.  But  I  soon  saw  the  necessity  of 
an  exliaustive  preliminary  investigation.  An  exact  knowl- 
edge of  the  way  in  which  new  species  arise  in  nature 


Mutations  in  Nature.  301 

seemed  to  me  to  be  an  indispensable  preliminary.  Hitherto 
this  phenomenon  had  not  been  observed  at  all,  in  the  nat- 
ural state.  I  had  to  postpone  the  plan  of  determining 
the  causes  of  these  processes.  Then  it  must  be  remem- 
bered that  our  knowledge  of  the  effects  of  crossing  was  at 
that  time  practically  nil\  and  such  knowledge  is  an  ab- 
solutely essential  condition  for  an  experimental  investi- 
gation of  the  phenomenon  itself.  It  was  imperative  that 
the  laws  of  hybridization  (especially  those  to  which  the 
Oenotheras  conform)  should  be  determined  first. 

For  these  reasons  I  have  postponed  an  investigation 
into  the  causes  of  mutation  until  these  preliminary  prob- 
lems were  well  on  the  road  to  solution. 

Tliere  are  two  ways  of  studying  mutation  in  the  field. 
The  first  is  to  look  for  and  collect  the  mutants  in  the 
place  where  the  parent  grows.  The  second  is  to  collect 
the  seed  in  the  field  and  to  grow  it  under  as  favorable 
circumstances  as  possible. 

It  will  be  immediately  evident  what  an  incomplete 
method  the  first  one  is,  and  how  much  superior  to  it  is 
the  second.  For  the  mutation  must  obviously  already 
liave  taken  place  in  the  seed ;  all  that  germination  does 
is  to  bring  it  before  our  eyes.  Consider  what  a  vast 
number  of  seeds  perish  during  the  first  few  days  after 
germination,  or  even  during  the  first  weeks,  when  they 
are  left  to  nature ;  especially  in  the  case  of  the  weaker 
seeds,  which  perhaps  may  contain  the  greater  number  of 
the  mutants.  An  average  plant  of  Oenothera  La- 
marckiana,  growing  wild,  often  has  over  a  hundred  fruits 
and  each  fruit  contains  from  one  to  two  hundred  seeds. 
Therefore  even  in  times  of  rapid  multiplication  it  is  only 
a  very  small  percentage  of  the  seedlings  which  grow  to 


302 


The  Pedigree  Families. 


their  full  stature.  So  that  even  if  the  plants  do  give 
rise  to  ever  so  many  mutations  in  their  seeds,  there  is 
always  the  possibility  either  that  there  will  be  no  sign 


Fig.  55.     Oenothera  Laniarckiana.     An  entire  plant  with 
flowers  on  its  main  stem  and  lateral  branches. 

of  them  or  that  traces  of  them  will  only  be  discovered 
from  time  to  time.^ 

A  simple  and  certain  method  of  discovering  whether 

*  Sur  I'introduction  de  I'Oenothera  Lamarckiana  dans  les  Pays- 
Bas.     Nederl.  Kruidk.  Archief,  Aug.  1895. 


Mutations  in  Nature.  303 

a  given  species  in  a  certain  locality  is  in  a  mutable  con- 
dition is  to  collect  its  seeds  and  sow  them.  The  sowing- 
should  be  carried  out  on  a  large  scale.  A  whole  series 
of  experiments,  which  I  have  started  with  a  number  of 
different  species  with  this  end  in  view,  have  been  without 
any  positive  result.  From  which  I  conclude  that  muta- 
tions in  nature  are  rare ;  although  I  am  convinced  that 
they  will  be  found  from  time  to  time  if  they  are  carefully 
looked  for. 

I  have  for  many  years  applied  both  these  methods  to 
the  case  of  Oenothera  Lamarckiana.  I  have  visited  the 
field  itself  almost  every  year,  or,  if  not,  have  had  it  vis- 
ited by  others.  The  majority  of  the  new  forms  have 
been  observed  in  that  way,  but  usually  as  weak  seedlings 
or  young  rosettes;  and  very  rarely  indeed  in  flower. 
Furthermore  I  have  collected  seed  in  the  field,  especially 
in  the  period  1886-1888,  when  I  began  my  experiments, 
and  have  sown  it  in  my  experimental  garden;  in  the 
first  two  years  in  small  quantities,  but  in  the  last  one  on 
a  large  scale.  Since  then  I  have  repeated  the  experiment 
from  time  to  time  and  only  stopped  when  I  was  pretty 
certain  what  would  happen. 

I  shall  now  give  a  list  of  the  various  species  which 
I  either  found  in  the  field  at  Hilversum  or  raised  from 
seeds  which  I  collected  there. 

Oenothera  lata.  In  1887  I  raised  three  examples  of 
lata  which  were  all  annual  from  seeds  which  I  gathered 
in  the  autumn  of  1886  from  quinquelocular  fruits  of 
otherwise  normal  Lamarckiana  plants.  Two  stayed  in 
my  garden  and  gave  rise  to  one  of  the  /afa-families  de- 
scribed in  §  7  (p.  288)  ;  the  third  germinated  with  three 
cotyledons  and  was  transplanted  to  a  garden  near  Hil- 
versum where  it  flowered  but  did  not  set  fertile  seed. 


304  The  Pedigree  Families. 

In  the  autumn  of  1888  I  raised  in  my  garden,  from 
seed  gathered  from  apparently  normal  examples  in  the 
field,  besides  numerous  Lamarckianas  seven  examples  of 
Jata',  of  which  four  developed  stems,  one  remained  in 
the  rosette  stage,  whilst  the  two  others  did  not  come  up 
till  late  in  the  summer.  In  the  same  summer  I  found  a 
beautiful  flowering  specimen  of  Jata  in  the  field  and  one 
or  two  other  young  plants  which  were  immediately  rec- 
ognizable as  belonging  to  this  new  species. 

In  1894  two  flowering  plants  and  one  rosette  of  lata 
were  again  found  in  the  field. 

0.  cUiptica.  I  found  one  rosette  in  1886  and  another 
was  found  in  1894. 

O.  nanella  was  obtained  in  1889  from  seed  collected 
in  the  field  in  the  previous  autumn :  there  were  three 
rosettes  which  however  did  not  survive  the  winter.  One 
of  these  was  a  lata-nanella;  that  is  to  say  it  combined 
the  characters  of  both  forms,  a  phenomenon  which  has 
occurred  again  in  my  experiments.  Another  dwarf  was 
found  in  the  field  at  Hilversum  in  1894. 

0.  nihrinervis.  One  rosette  was  raised  from  the 
seed  collected  in  1888,  which  has  been  so  often  referred 
to  already. 

O.  spathnlata.  This  form  was  collected  as  a  rosette 
in  the  field  at  Hilversum  in  1886  and  1894. 

Five  of  the  new  species  therefore,  either  appeared 
in  the  field  at  Hilversum  or  from  seed  collected  there. 
They  appeared  rarely,  but  repeatedly,  and  moreover  their 
appearance  extended  over  the  course  of  several  years. 
It  was,  however,  not  possible  for  the  ones  that  arose 
later  to  have  descended  from  the  earlier  ones,  since  the 
latter  had  not  flowered. 


Mutations  in  Nature.  305 


The   foregoing  account  may  be  summarized   in  the 
following  list. 


SUMMARY   OF    NEW    SPECIES    FOUND   AT    HILVERSUM. 

PLANTS  FROM  SEED 

O.  lata  1889,  1894  O.  lata  1887,  1889 

O.  nanella  1894  O.  naiiella  1889 

O.  spathulata  1886,  1894  O.  laia-nanella  1889 

O.  elliptica  1886  O.  rubrinervis    1889 

This  list  contains  just  those  forms  which  are  the 
most  easily  recognizable  and  appeared  oftenest  in  my  cul- 
tures. Of  the  rest  the  only  one  which  has  occurred  in 
my  garden  up  to  the  year  1894,  (the  last  year  in  the  above 
list),  was  0.  scintillans  and  this  only  in  one  specimen. 

These  forms  therefore  clearly  originated  in  the  field 
and  not  in  my  cultures.  Moreover  they  arose  there  in 
the  same  way  as  in  my  experimental  garden,  without 
transitional  stages,  from  the  seeds  of  normal  Larnarc- 
kiana,  and  year  after  year. 

These  observations  do  not  pretend  to  be  complete 
but  they  suffice  to  demonstrate  the  identity  of  the  pro- 
cesses in  the  field  and  in  the  garden.  The  cultures  are 
merely  a  more  convenient  and  certain  method  of  dis- 
covering what  happens  in  nature. 

Whether  O.  scintillans  and  the  other  species  which 
were  only  observed  in  my  garden  also  appeared  from 
time  to  time  in  the  field  at  Hilversum,  I  do  not,  of  course, 
know.  But  I  regard  it  as  extremely  probable  that  they 
did.  Several  of  them  appeared  so  rarely  in  my  garden 
that  it  did  not  seem  worth  while  to  try  to  get  them  again 
by  carrying  out  more  extensive  sowings.  Still  less  did 
it  seem  likely  that  I  could  get  them  by  sowing  seed  col- 
lected in  the  open. 


306  The  Pedigree  Families. 

There  is  no  reason  to  suppose  that  the  first  record  of 
a  new  species  corresponds  with  its  first  appearance.  I 
found  0.  elliptica  and  O.  spatJiidata  the  first  year  that  I 
visited  the  place  (in  1886)  ;  I  found  O.  lata  the  year 
after.  It  is  very  probable  indeed  that  these  and  other 
forms  have  also  appeared  in  previous  years  either  as 
young  plants  or  as  seeds, 

I  am  convinced  that  the  mutations  of  our  Evening 
Primrose  were  already  in  full  swing  when  I  began  my 
observations  and  experiments,  and  that  I  did  not  catch 
it  in  the  act  of  beginning  to  give  rise  to  new  species. 
I  simply  discovered  how  the  new  forms,  which  though 
in  a  latent  condition  were  already  there,  came  to  light 
from  time  to  time. 

The  beginning  of  the  process  of  the  origin  of  a  new 
species  will  escape  observation  so  long  as  it  is  impossible 
to  induce  mutations  at  will.  And  it  is  not  likel}^  that  we 
shall  be  able  to  do  that  for  a  long  time. 

The  fact  that  two  subspecies  already  existed  at  Hil- 
versum  in  1886  in  full  development  speaks  strongly  in 
favor  of  the  view  that  0.  Lamarckiana  was  at  that  time 
already  in  a  mutable  phase.  The  two  species  I  am  re- 
ferring to  are  the  O.  laevifolia  and  O.  hrevistylis.  In 
1886  I  found  two  examples  of  the  latter  in  flower;  the 
former  I  found  in  the  same  year  as  rosettes  which  flow- 
ered in  1887  and  provided  the  seed  for  the  laevifolia- 
family  described  above.  Inasmuch  as  these  two  new 
species  had  not  been  observed  anywhere  else  it  is  reason- 
able to  believe  that  they  arose  on  the  spot.  This  view  is 
supported  by  the  circumstance  that  I  first  found  only 
a  few  examples  of  each  of  the  two  species,  each  in  a  little 
group  to  itself;  0.  laevifolia  in  the  northwest,  and  O. 
hrevistylis  at  the  northeast  corner  of  the  field.     Whether 


Mutations  in  Nature.  307 

they  had  arisen  a  short  or  a  long  time  back  cannot  be 
determined  now.  That  they  were  able  to  maintain  them- 
selves, whilst  the  other  species  were  not,  is  probably  due 
to  the  fact  that  during  the  seedling  and  rosette  stages 
they  are  not  in  any  way  inferior  to  the  ordinary  Even- 
ing Primrose. 

And,  lastly,  the  question  arises  whether  the  mutation 
period  which  I  observed,  began  in  the  field  at  Hilversum 
or  before.^  The  rapid  multiplication  of  the  plant  in  the 
field  since  it  was  first  sown  in  1870  would  appear,  ac- 
cording to  horticultural  experience,  to  be  a  sufficient  cause 
of  mutation.  Within  about  8  generations  (1870-1886) 
the  plants  had  increased  from  one  or  two  to  many  hun- 
dreds which  had  scattered  their  seeds  far  and  wide. 

Perhaps  the  mutation  period  was  much  older,  if  not 
in  the  case  of  all  the  new  forms  at  least  in  that  of  those 
which  appeared  oftenest  (for  example  0.  lata  and  O. 
nanella).  But  as  I  did  not  witness  the  beginning  of  this 
process  it  does  not  seem  to  me  to  matter  much  when  and 
where  it  happened. 

.  The  point  is  that  the  cultures  in  the  garden  disclose 
to  us  what  happens,  but  ordinarily  escapes  observation, 
in  nature. 

^  Later  experiments  have  shown  the  mutation  period  to  be  much 
older.  Cf.  Ueber  die  Dauer  der  Miitationspcriode  bet  Oenothera 
Lamarckiana,  Ber.  d.  d.  bot.  Ges.,  1905,  Bd.  XXIII,  p.  382.  (Note 
of  1908.) 


II.   THE  ORIGIN  OF  EACH  NEW  SPECIES  CON- 
SIDERED SEPARATELY. 

A.  THE  TWO  OLDER  SPECIES. 

§  10.    OENOTHERA  LAEVIFOLIA. 

The  reader  will  remember  that  amongst  the  Evening 
Primroses  in  the  field  at  Hilversnm  there  grew  two  new 
species,  0.  laevifolia  and  0.  brevistylis.  These  forms 
have  not  been  observed  anywhere  else  before,  so  far  as 
I  have  been  able  to  ascertain.  It  follows  that  they  must 
have  arisen  either  on  the  spot  (that  is  after  1870)  or  at 
some  period  before  the  introduction  of  the  parent  species. 
They  have  maintained  themselves  in  the  locality  ever 
since  I  began  to  observe  them  but  there  are  no  means 
of  telling  whether  a  race  of  them  has  existed  since  they 
first  arose,  or  whether  they  have  been  produced  by  the 
Lamarckiana  from  time  to  time. 

They  have  never  arisen  in  my  cultures.  I  have  spent 
much  labor  in  looking  for  them ;  but  in  vain.  O.  brevi- 
stylis cannot  possibly  be  missed  if  it  is  there  and  I  have 
carefully  searched  the  plots  for  O.  laevifolia.  For  ex- 
ample in  1895  I  looked  through  over  one  thousand  flow- 
ering plants  of  the  Lainarckiana-iRmWy  without  seeing 
a  trace  of  a  smooth  leaved  form.  I  repeated  the  search 
in  later  years  when  I  had  many  thousands  of  flowering 
Oenotheras  under  cultivation. 


Oenothera  Laevifolia. 


09 


I  have  often  brought  Oenothera  laevifolia  from  Hil- 
versum  to  Amsterdam,  sometimes  in  the  shape  of  seeds, 
sometimes  by  fertihzing  castrated  flowers  of  my  O.  La- 
viarckiana  with  laevifolia  pollen.  From  the  seeds  ripened 
at  Hilversum  I  obtained  in  1888,  for  example,  no  more 
than  2  %  laevifolia ;  in 
1895,  on  the  other 
hand,  about  50  %.  The 
former  number  is  ob- 
viously the  result  of 
the  rarity  of  the  spe- 
cies in  question  at  that 
time,  there  being  little 
chance  of  its  being  fer- 
tilized by  its  own  pol- 
len. 

The  distinguishing 
features  of  this  species 
are  to  be  found  partly 
in  the  leaves  and  partly 
in  the  flowers. 

The  leaves  of  Oeno- 
thera Lamarckiana  are 
rather  coarse,  an  effect 
produced  by  the  numer- 
ous crumples  which  dis- 
tort the  areas  between 
the  veins  and  especially 
those  areas  which  border  on  the  middle  region  of  the 
principal  veins.  They  are  caused  by  a  faulty  correla- 
tion between  the  growth  of  the  areas  and  of  the  veins; 
either  the  areas  grow  too  fast,  or  the  veins  elongate  too 
slowlv. 


Fig.  56.   Oenothera  laevifolia.   Top  of 
a  stem,  in  flower. 


310   Origin  of  Each  Species  Considered  Separately 


My  0.  laevi folia  does  not  possess  these  crumples;  the 
leaves  are  ahnost  flat  and  appear  therefore  of  a  more 
beautiful  and  uniform  green.  They  are  rather  narrower 
and  as  a  rule  somewhat  smaller  than  those  of  the  parent 
species,  although  the  difference  is  so  trivial  that  it  falls 
within  the  limits  of  individual  variation.  This  indicates 
that  the  absence  of  crumpling  is  due  to  a  diminished 
growth  of  the  areas  between  the  veins. 

Such  crumples  occur  not  only  in  0.  Lamarckiana 
but  in  some  of  the  new  species  that  have  arisen  from  it, 
for  example  O.  lata  and   0.  albida.     I  have  therefore 

figured  transverse  sec- 
tions of  these  leaves  in 
Fig.  57  as  being  the  best 
way  of  giving  an  idea  of 
the  extent  of  these  crum- 
ples.^ The  leaf  of  O. 
Lamarckiana  is  just  like 
that  of  O.  albida  in  this 
respect  whilst  the  leaves 
of  O.  lata  are  distorted 
much  more  (Fig.  58). 
The  leaves  of  0.  laevifolia  appear  in  transverse  section 
as  a  straight  line  from  which  the  nerves  project  here  and 
there. 

Incomplete  development  of  this  character  occurs  fairly 
often  in  O.  laevifolia  even  after  many  years  of  selection. 
A  smooth-leaved  plant  is  occasionally  met  with  posses- 

^To  make  these  figures  as  faithful  as  possible  I  have  embedded 
the  fresh  leaves  in  a  thick  slab  of  glycerin-gelatin,  and  when  this 
had  hardened  cut  them  in  it.  I  took  a  section  of  about  i  cm.  thick 
and  laid  on  it  a  dry  film  of  gelatin  on  which  I  traced  the  outline 
of  the  section  of  the  leaf.  If  I  had  simply  cut  strips  from  the  leaf 
or  had  tried  to  deal  with  thinner  sections,  many  of  the  crumples 
would  inevitably  have  disappeared. 


Fig.  57.  Transverse  sections  of  leaves 
to  show  the  crumples.  Vs  nat.  size. 
I,  Part  of  a  leaf  of  O.  lata.  2, 
Transverse  section  through  whole 
leaf  of  O.  lata.  3,  The  same  of  O. 
albida.     m,  median  veins. 


Oenothera  Laevifolia. 


311 


sing  occasional  crumples  on  its  leaves  and  sometimes 
whole  leaves  covered  with  them.  Or  again  the  smooth- 
ness of  the  leaves  gradually  de- 
creases from  the  top  of  the  stem 
downwards.  It  even  happens 
sometimes  that  it  is  impossible  to 
draw  a  sharp  line  of  demarcation 
between  Lamarckiana  and  the 
smooth  leaved  plants,  or  to  cal- 
culate the  percentage  of  the  lat- 
ter. 

When  it  was  possible  to  allow 
not  merely  the  main  stem  of  the 
plant  to  grow  (which  was  all  I 
could  do  as  a  rule,  through  lack 
of  space)  but  also  the  lateral 
branches  which  spring  from  the 
axils  of  the  radical  leaves  it  was 
found  that  the  laevifolia-charac- 
ters  were  better  developed  in  the 
leaves  of  the  branches  than  in 
those  of  the  main  stem.  In  such 
cases  these  were  often  useful  in 
identifying  the  plant. 

O.  laevifolia  has  obviously  in- 
herited the  occasional  crumples 
which  it  possesses,  from  its  parent 
species;  they  can  be  regarded  as 
rudimentary  or  atavistic  charac- 
ters.^ Closer  study  will  probably 
prove  such  relics  to  be  much  commoner  in  nature  than 


Fig.  58.  Radical  leaf  of 
a  rosette  of  O.  lata, 
viewed  from  the  dor- 
sal side,  to  show  the 
numerous  unevennesses 
(crumples)  on  its  sur- 
face. 


*Like  the  stalked  leaves  of  the  young  plants  of  O.  nanella.     See 
§  18  and  the  tables  in  §  27  of  this  part. 


312   Origin  of  Each  Species  Considered  Separately. 


is  generally  supposed.    They  belong  to  the  same  category 
as  Delpino^s  subvariations.^ 

These  crumples  occur  in  many  other  plants.  They  are 
sometimes  regarded  as  useful  adaptations.  "The  more 
the  form  of  the  leaf  surface  is  adapted  for  retaining 
water  resulting  from  rain  or  thaw  by  trough-  or  cup- 
shaped  depressions  in  its  surface,"  says  Von  Rumker,^ 


Fig.  59.  Oenothera  laevifolia.  Flowers  with  narrow  petals ; 
a,  seen  from  the  side;  b,  seen  from  above;  c  and  d,  iso- 
lated petals  spread  out.  In  a  one  of  the  petals  has  been 
removed,    a,  c,  d  taken  in  1894,  b>  i"  1899. 

"the  longer  can  the  plant  keep  the  water  for  its  own 

use."    How  far  O.  laevifolia  is  inferior  to  other  Evening 

Primroses  from  its  lacking  these  depressions  is  not  an 

easy  question  to  answer;  but  this  much  is  certain  that  I 

have  always  found  it  weaker  and  smaller  than  the  parent 

species.     In  the  experimental  garden  however  where  the 

\  The  deviations  from  the  type  of  leaf,  characteristic  of  the 
species,  which  often  occur  at  the  bottom  of  branches  are  classified 
by  Delpino  as  subvariations.  See  Delpino,  Teoria  generate  delta 
Fillotassi,  1883.     They  are  often  of  an  atavistic  natuir 

^VoN  RiJMKER^  Zuckerruhensiichtung,  1894,  P-  6. 


Oenothera  Laevi folia.  313 

plants  never  lack  water  this  character  makes  no  differ- 
ence. 

A  very  characteristic  feature  of  O.  laevifolia  is  af- 
forded by  the  flowers  on  the  weaker  shoots.  They  have 
narrow  petals  which  exhibit  every  transition  from  the 
broad,  obcordate  contour  of  those  of  the  strongest  flowers 
to  oval  or  elliptical  forms  as  shown  at  c  and  d  in  Fig.  59. 

This  character  is  very  constant.  It  was  through  it, 
that  I  first  discovered  the  new  form  and  it  was  only 
after  this  had  been  in  cultivation  for  some  time  that  I 
became  acquainted  with  the  smooth  leaves.  Weak  plants 
bear  such  flowers  on  the  main  stem ;  stronger  ones  either 
on  the  whole  extent  or  only  at  the  base  of  the  lateral 
branches. 

In  the  height  of  summer  these  flowers  are  rare ;  but 
towards  autumn  and  often  as  early  as  the  beginning  of 
September  they  appear  in  greater  numbers.  By  cultivat- 
ing only  healthy  plants  without  lateral  branches  it  would 
be  possible  for  a  whole  year  to  go  by,  without  seeing  one 
of  these  flowers :  this  has  sometimes  happened  in  my 
experiments. 

There  is  something  extraordinarily  attractive  about 
these  flowers.  They  are  smaller  and  neater  than  the 
rather  gross  and  stout  flowers  of  the  common  Evening 
Primrose;  their  color  is  often  paler;  their  form,  in  a 
sense,  freer,  inasmuch  as  the  petals  scarcely  touch  one 
another.  I  have  often  stuck  them  into  my  journal  or 
photographed  them.  I  have  found  them  from  1887  up 
to  the  present  day,  always  the  same,  exhibiting  the  same 
varieties  of  form  but  without  progressing  in  any  one 
particular  direction,  just  like  all  the  other  new  species 
which  have  proved  constant  in  all  their  characters  from 
their  origin. 


314  Origin  of  Each  Species  Considered  Separately. 

The  forms  of  the  petals  of  a  single  flower  often  differ 
from  one  another  (Fig.  59  b).  The  petals  of  plants 
grown  in  the  field  on  dry  sand  were  narrower  than  those 
of  plants  grown  in  the  garden  on  manured  soil.  The 
petals  of  the  former  were  almost  twice  as  long  as  broad, 
in  those  of  the  latter  the  relation  of  length  to  breadth 
was  as  2  to  3.  The  emarginate  character  of  the  normal 
petals  is  absent  in  them;  the  petals  are,  on  the  contrary, 
obtusely  rounded.  Their  greatest  breadth  is  in  the  middle. 
The  narrowest  petals  that  I  have  observed  were  three 
centimeters  long  and  one  broad.  But  as  I  have  already 
stated  there  exists  a  complete  series  of  transitions  be- 
tween these  and  the  obcordate  ones  of  strong  flowers. 

Oval  petals  are  by  no  means  confined  to  O.  laevi folia. 
They  occur  regularly  on  O.  elliptic  a.  I  have  also  some- 
times found  them  on  weak  shoots  of  0.  biennis. 

In  the  other  characters  0.  laevifolia  is  very  much 
like  O.  Lamarckiana,  not  differing  from  it  in  any  essen- 
tial features  save  those  already  mentioned.  The  plants 
are  about  the  same  size.  So  are  the  flowers  and  fruits 
and  general  habit.  Nevertheless  a  bed  of  0.  laevifolia, 
even  if  it  is  some  distance  away  can  always  be  recog- 
nized from  a  group  of  Lamarckiana  by  characters  which 
may  be  manifested  to  a  greater  or  lesser  degree  but 
which  always  tend  in  the  same  direction.  The  color  of 
the  flowers,  especially  of  the  later  ones,  is  usually  a  little 
paler;  the  buds  a  little  thinner,  the  bracts  of  the  inflor- 
escence a  little  narrower  and  the  whole  plant  more  deli- 
cate and  neat. 

During  the  first  few  years  of  its  cultivation  I  used 
to  allow  O.  laevifolia  to  cross  freely  with  O.  Lamarckiana 
for  reasons  which  I  have  mentioned  above  (§6).  But 
since  1894  I  have  excluded  the  visits  of  insects  by  en- 


Oenothera  Brevistylis.  315 

closing  the  flowers  in  parchment  bags ;  and  fertiHzed  them 
with  their  own  pollen.  Since  that  time  the  species  has 
proved  absolutely  constant;  and  each  year  I  choose  the 
best  examples  with  the  smoothest  leaves  as  seed-parents. 


§  II.    OENOTHERA  BREVISTYLIS. 

This  form  has  been  thoroughly  investigated  and  de- 
scribed by  Julius  Pohl.^  I  have  used  it  mainly  in  hy- 
bridization experiments,  in  which  it  behaves  in  a  different 
way  from  all  other  species  in  the  group  of  the  evening 
primroses.  I  shall  deal  here  only  with  its  external  char- 
acters, with  its  first  discovery  in  the  field  and  with  its  con- 
stancy. This  species,  which  is  very  easily  recognized  dur- 
mg  its  flowering  period,  has  never  arisen  in  my  cultures. 

In  the  rosette  stage  and  in  fact  at  any  time  before  it 
flowers,  it  is  difficult  to  distinguish.  Its  more  rounded 
leaves  give  it  a  slightly  different  appearance;  and  in  hy- 
brid cultures  it  is  often  possible  before  any  stems  have 
been  developed  to  predict  whether  there  will  be  many  or 
few  brevistylis.  But  it  is  not  until  the  flower  buds  appear 
on  the  stem  that  the  difference  between  it  and  other  forms 
becomes  clearly  discernible,  and  that  one  can  record  them 
with  safety.  The  young  inflorescence  forms  a  rosette  of 
rounded  leaves  on  the  top  of  the  stem  in  O.  brevistylis 
and  of  pointed  ones  in  O.  Lamarckiana.  Shortly  after- 
wards the  buds  appear;  they  are  shorter,  thicker  and 
blunter  than  the  slender  conical  ones  of  the  parent  spe- 
cies. Then  the  flowers  open,  just  as  large  and  just  as 
beautiful  as  in  Lamarck's  Evening  Primrose.  At  first 
sight  it  looks  as  if  they  had  neither  a  style  nor  stigma; 

*  Julius  Pohl,  Ueher  Variationsweite  bei  Oenothera  Lamarckiana, 
Oester.  bgt.  Zeitschrift,  Jahrgang  1895,  Nos.  5  and  6,  Tafel  X. 


316   Origin  of  Each  Species  Considered  Separately. 

but  closer  inspection  reveals  them  hidden  away  in  the 
tube  at  the  base  of  the  corolla.  Hence  the  name  O.  brevi- 
stylis  or  short-styled  Evening  Primrose.  The  length  of 
the  style  varies  very  much;  the  stigmas  sometimes  lie 
right  inside  the  tube,  sometimes  they  stand  a  full  centi- 
meter out  of  it.  But  there  is  a  great  gap  between  the 
longest  styles  of  0.  brevistylis  and  the  shortest  ones  of 
O.  Lamar ckiana. 

When  the  flowers  are  through  blooming  they  wither 
down  as  far  as  the  fruit  but  are  not  thrown  off  as  they  are 
in  0.  Laniarckiana,  but  remain  attached  for  considerable 
time  to  the  unripe  fruit.  The  plants  can  be  recognized 
from  afar  by  this  character,  and  even  perhaps  still  more 
readily  by  the  smallness  of  their  fruits.  In  their  fully 
developed  state  these  are  hardly  larger  than  the  ovaries 
of  open  flowers ;  they  remam  bent  outwards,  pressed 
against  the  bract  and  almost  hidden  between  the  broad 
auricles  at  its  base.  From  a  distance  it  looks  as  if  the 
plant  had  never  been  fertilized:  LamarcHawa  on  the  other 
hand  does  not  hide  its  great,  fine,  erect  fruits  between  the 
bracts.  (Plate  I.) 

In  the  fruiting  period  Brevistylis  plants  can  therefore 
be  more  easily  recognized  than  those  in  blossom;  but  as 
a  rule  brevistylis  keeps  up  flowering  later  into  the  autumn 
than  O.  Laniarckiana. 

The  stigmas  are  developed  in  an  unusual  way;  for 
instead  of  being  stout  and  cylindrical  they  are  flattened 
and  leaf-like.  They  retain  the  abundance  of  pollen  that 
is  brought  to  them  by  bumblebees,  permit  the  develop- 
ment of  pollen  tubes  which  elongate  in  the  usual  way,  and 
reach  the  ovary  in  numbers  but  fertilize  only  very  few 
ovules.     Many  plants  set  no  seed  at  all,  others  very  little. 


Oenothera  Brevistylis.  317 

The  ovary  extends  a  little  above  the  insertion  of  the 
corolla  up  into  the  style. 

O.  brevistylis  was  the  first  sub-species  of  Oenothera 
Lamarckiana  which  I  discovered.  I  found  it  in  August 
of  the  first  year  of  my  investigations,  1886,  when,  as 
already  stated  (p.  266)  it  occupied  a  little  corner  in  the 
northeast  of  the  field.  There  were  two  individuals,  one 
where  the  plants  grew  thickest,  the  other  on  a  spot  about 
one  hundred  paces  away.  Both  were  well  developed, 
flowering  from  many  shoots  and,  as  far  as  I  could  judge, 
biennial.  I  found  them  on  the  25th  of  August.  They 
caught  my  eye  from  quite  a  distance  by  the  almost  com- 
plete absence  of  any  fruit  on  them.  This  character  made 
it  easy  to  be  certain  that  only  these  two  had  been  short- 
styled  when  in  flower,  for  all  the  others  had  set  normal 
fruits. 

In  1889,  the  part  of  the  field  in  which  these  two  short- 
styled  plants  stood  was  well  cleaned  and  dug  up;  never- 
theless, towards  the  end  of  July  of  that  year  I  found  a 
group  of  12  short-styled  individuals  nearly  in  the  middle 
of  the  field  on  a  spot  where  not  a  single  Oenothera  grew 
in  1886.  The  new  species  has  since  maintained  itself  on 
this  spot  and  it  has  been  observed  there  nearly  every 
year.  In  the  summer  of  1894  I  saw  six  plants  there  in 
flower;  in  August  of  1898  they  were  fairly  numerous, 
but  since  then  they  have  appeared  only  sporadically. 

Before  1895  I  thought  O.  hrevistyUs  incapable  of 
setting  seed;  for  I  regarded  it  as  being  solely  male.  In 
1895  I  collected  lots  of  fruits  and  got  a  meagre  quantity 
of  seed  which  seemed  to  me  to  be  empty,  so  that  I  did 
not  sow  it  in  the  following  spring,  but  when  in  the  fol- 
lowing autumn  I  had  gone  over  my  cultures  thoroughly 
I  came  to  the  conclusion  that  it  might  be  worth  while  to 


318   Origin  of  Each  Species  Considered  Separately. 

sow  the  seed.  Of  the  whole  quantity  of  seed  borne  by 
200  fruits  there  germinated  a  httle  over  300  seeds.  That 
is  1  to  2  seeds  per  fruit.  The  mother  plants  had  grown 
amongst  other  kinds  and  were  fertilized  by  bumblebees 
and  therefore  largely  crossed.  Nevertheless  of  the  83 
flowering  plants  to  which  this  seed  gave  rise  69  or  83  % 
were  O.  hrevistylis. 

This  result  encouraged  me  to  try  artificial  self-fertili- 
zation in  parchment  bags.  For  this  purpose  I  chose  in 
1897  those  plants  whose  stigmas  projected  farthest  out 
of  the  tubes;  for  I  had  satisfied  myself  that  as  a  rule 
these  furnished  the  largest  fruits.  I  harvested  seeds  from 
five  plants.  In  1898  I  sowed  the  seed  of  each  plant 
separately.  Nearly  all  the  young  plants  flowered  between 
August  and  October;  they  were  all,  without  exception, 
short-styled.  Altogether  there  were  175;  some  in  flower 
and  some  only  with  buds,  in  which,  however,  I  was  able 
to  observe  the  length  of  the  style. 

Oenothera  hrevistylis,  therefore,  when  self-fertilized, 
is  absolutely  constant  in  spite  of  its  comparative  sterility. 


B.    THE  CONSTANT  NEW  SPECIES. 

§  12.   OENOTHERA  GIGAS. 

(Plate  II.) 

Oenothera  gigas  is  at  once  the  finest  and  rarest  new 
species  that  has  arisen  in  my  cultures.  Whereas  most  of 
the  new  forms  are  weaker  than  the  parent  species  this 
one  is  almost  in  every  respect  stronger  and  bigger  and 
more  heavily  built.  A  comparison  of  Plates  I  and  II 
will  show  at  a  glance  the  nature  of  the  difference  be- 
tween gigas  and  Lamarckiana ;  both  represent  the  top  of 


Oenothera  Gigas.  319 

the  main  stem  in  September,  by  which  time  the  lower 
fruits  are  fully  grown.  The  top  of  the  plant  still  bears 
a  head  of  flowers  and  buds.  Figures  60  and  61  repre- 
sent the  same  two  forms  at  the  beginning  of  the  flower- 
ing period. 

In  warm  weather  the  flowers  of  the  Evening  Prim- 
roses open  in  the  evening  usually  at  a  rate  of  2  or  3  a 
day,  seldom  more  and  sometimes  fewer  according  to  the 
weather.  They  are  pollinated  by  bumblebees  and  by 
Noctuidae  {Pliisia  gamma,  Agrofis  segetiim  and  others) 
and  as  a  rule  wither  during  the  night.  The  beauty  of  the 
flowers  has  completely  disappeared  by  the  following- 
morning.  It  is  only  in  cool  or  even  cold  weather  that 
the  flowers  remain  open  till  the  following  day;  but  even 
then  they  seldom  last  on  into  the  evening. 

The  opening  of  the  flowers  has  been  described  by 
E.  RozE.^  The  event  is  a  very  remarkable  one.  Early 
on  a  beautiful  summer  evening,  when  the  plants  bear 
nothing  but  buds  and  dead  flowers,  while  one  may  be 
busied  with  other  operations  in  the  garden,  one  looks 
round  and  suddenly  sees  every  plant  in  blossom.  Half 
an  hour  suffices  to  change  the  whole  aspect  of  the  gar- 
den. 

The  process  of  opening  is  in  preparation  all  day.  The 
buds  become  yellow ;  their  anthers  have  completely  de- 
hisced. The  tops  of  the  sepals  are  still  joined  together 
to  form  an  entire  cap  which  however  becomes  split  lower 
down  during  the  course  of  the  day.  The  petals  gradually 
swell  until  at  last  they  veritably  burst  the  calyx  open, 
throw  the  sepals  backwards  and  unfold  their  free  ends. 
The  whole  thing  happens  in  a  few  minutes  or  seconds. 

*  E.  RozE.  U epanouissement  de  la  Heur  de  VOenothera  suaveolcns 
Desf.     Bull.  Soc.  bot.  France.     T.  XLII,  8  Nov.  1895,  p.  575. 


320   Origin  of  Each  Species  Considered  Separately. 


The  petals  now  stand  out  in  the  form  of  a  cross;  their 
inner  halves  being  still  rolled  up  together.     But  it  is  not 


Fig.  60.  Oenothera  gigas.  Top  of  a  stem  just  beginning  to 
flower.  A  petal  has  been  removed  from  the  flower  a. 
h,  a  withering  flower. 

long  before  these  unfold  and  set  the  anthers  and  the 
style  free. 

My  new  species  agree  in  all  these  points  with  the 


Oenothera  Gigas. 


321 


parent  species  and  its  related  forms,  0.  biennis  and  so 
forth. 

One  of  the  most  distinctive  features  of  Oenothera 
gigas  hes  in  the  breadth  of   the  petals.     The  swollen 


Fig.  6i.  Oenothera  Lamarckiana.  Top  of  a  stem  begin- 
ning to  flower,  a,  the  lowest  flower  withered  and  fallen 
down  on  the  bract. 

character  of  the  buds  is  due  to  this  feature;  as  also  is 
the  cup-like  shape  of  the  base  of  the  open  flowers.  The 
petals  in  this  species,  as  in  Lamarck's  Evening  Primrose, 


322   Origin  of  Each  Species  Considered  Separately. 

are  obcordate  and  more  or  less  deeply  emarginate  at  their 
broad  apices.  In  both  species  the  petals  are  about  3  cm. 
long;  but  in  O.  Lamarchiana  they  are  5  cm.  broad,  whilst 
in  O.  gigas  they  are  6  cm, 

I  did  not  find  any  other  differences  worth  mentioning 
in  the  absolute  or  relative  dimensions  of  the  flowers. 
The  size  of  the  flowers  of  both  species  gradually  de- 
creases as  autumn  comes  on,  a  fact  which  must  be  borne 
in  mind  when  we  are  looking  for  constant  differences 
between  the  two.  The  same  is  true  of  the  calyx  tube  and 
of  the  tip  of  the  calyx,  of  the  height  of  the  stigma  and  of 
the  anthers  and  so  forth.  Speaking  broadly  gigas  is  more 
compact  than  Lamarckiana ;  and  though  its  flowers  do  not 
exceed  those  of  its  parent  species  in  number,  they  form  a 
denser  and  therefore  more  beautiful  head  on  the  stem. 

The  fruits  of  0.  gigas  are  very  different  from  those 
of  O  Lamarckiana :  they  are  half  as  long  but  about  as 
stout.  The  seeds  are  on  this  account  less  numerous; 
but  they  are  larger  and  heavier. 

Oenothera  gigas  is  stronger  than  the  other  species  in 
almost  every  respect.  This  is  seen  most  strikingly  in 
the  girth  of  the  stem  as  shown  in  Plates  I  and  II  and  in 
figures  60  and  61.  The  stem  is  stronger  right  from  its 
base,  and  for  that  reason  grows  more  vertically  upwards 
— a  feature  which  greatly  facilitates  the  recognition  of 
the  young  plants.  In  the  flowering  region  the  diameter 
of  the  stem  is  almost  twice  as  large  as  it  is  in  O.  La- 
marckiana, in  which  it  is  at  most  5-6  mm. :  in  gigas  it  is 
often  10  mm. 

The  whole  stem  is  much  more  thickly  beset  with 
leaves  and  the  leaves  themselves  are  broader,  more  nu- 
merous, and  more  or  less  recurved.  The  great  number 
of  leaves  is  due  to  the  shortness  of  the  internodes ;  in  the 


Oenothera  Gig  as. 


323 


flowering  part  of  the  stem  I  found  the  length  of  the 
internode  between  two  nearly  ripe  fruits  to  be  barely 
0 . 5  cm.  Moreover  the  leaves  are  broader,  the  bracts 
bigger  and,  for  this  reason,  the  whole  fruit-bearing  spike 
less  naked. 


Fig.  62.  Full  grown  radical  leaves  in  August  to  show  the 
difference  in  breadth.  L,  Oenothera  Lamarckiana;  G, 
Oenothera  gigas. 

I  recognized  the  species,  when  I  first  saw  it  in  my 
cultures  in  1896,  by  its  short  stumpy  fruits  crowded  to- 
gether and  also  by  its  cup-shaped  flowers. 


324  Origin  of  Each  Species  Considered  Separately, 

Although  ^z^a^-plants  can  be  recognized  before  they 
flower  it  is  difficult  to  give  an  accurate  description  of 
their  leaves  because  they  exhibit  a  high  degree  of  indi- 
vidual variability — much  greater  in  fact  than  do  those 
of  the  parent  species.  The  greater  breadth  is  the  chief 
difference;  the  length  and  general  shape  are  about  the 
same.  The  leaves,  moreover,  of  gigas  are  more  crumpled 
(compare  page  310  and  Fig.  62).  But  the  breadth 
which  is  usually  a  matter  of  4-6  cm.  sometimes  sinks  to 


Fig.  6s.    Oenothera  gigas.    A  young  plant  in  June,  a  few 
days  before  transplanting,   (V2). 

2  cm.  without  however  destroying  the  characteristic  look 
of  the  species.  The  leaves  of  the  stem  are  usually  set  on 
a  shorter  stalk  and  are  more  deeply  toothed  than  in  O. 
Lamarckiana.  The  branches,  of  which  a  great  many 
develop,  remain  sessile  in  the  axils  of  the  leaves  as  short 
densely  foliate  spikes  which  tend  to  make  the  foliage  on 
the  stem  much  thicker,  just  as  in  O.  ohlonga  (Fig.  71). 
The  difference  between  the  young  rosettes  in  June 
(when  they  are  usually  planted  out)    is  very  striking. 


Oenothera  Gigas. 


325 


The  cotyledons  are  at  that  time  still  present;  but  dying 
off;  or  perhaps  already  dead.  Figures  63  and  64  repre- 
sent two  plants  at  this  age  reduced  to  the  same  scale  (%). 
The  gigas  rosettes  are  compact,  round  and  stout;  the 
Lamarckianas  are  looser,  their  leaves  have  longer  petioles 


Fig.  64.  Oenothera  Lamarckiana.  A  young  plant  in  June, 
a  few  days  before  transplanting  (V2)  ;  c,  the  cotyledon- 
ary  leaves. 


and  therefore  make  less  use  of  the  space  of  ground  at 
their  disposal.^ 

Oenothera  gigas  has  only  appeared  once  in  my  cul- 
tures— a  single  specimen  in  1895.    The  event  has  already 

^  Miss  Anne  M.  Lutz  discovered  another  highly  interesting  dif- 
ference between  O.  Lamarckiana  and  O.  gigas  The  former  has  14 
chromosomes  in  its  nuclei,  like  O.  biennis  and  other  species,  but  the 
nuclei  of  O.  gigas  have  twice  as  many,  viz.,  28.  Cf.  Science,  Vol.  26, 
Aug.  2,  1907,  p.  151.,     (Note  of  1908.) 


326   Origin  of  Each  Species  Considered  Separately. 


been  described  in  §  3   (p.  227).     It  was  evident  that  it 
was  a  constant  species  directly  its  seeds  germinated.     As 


Fig.  65.     Seedlings  of  Oenothera  Lamarckiana    (L)    and 
O.  gigas  (G).    c,  the  cotyledons.    Magnitied;  the  natural 
size  shown  in  the  middle. 

soon  as  they  have  acquired  their  first  and  second  leaves 
the  seedlings   can   be   distinguished   from  those  of   the 

parent  species  with  perfect 
ease  (Figure  65).  Their 
leaves  are  not  only  broader 
but  more  or  less  markedly 
cordate  at  their  base.  The 
latter  character  is  gradu- 
ally lost  in  the  succeeding 
leaves  but  the  broader  base 
persists  for  some  time 
longer  as  a  convenient 
mark  of  identification  (Fig. 
66). 

This  character  made  it 
possible  for  me  to  demon- 
strate the  constancy  of  the 
new  species  in  the  second,  third  and  fourth  generations 
(1897,  1899,  1900)  without  having  to  grow  more  than 
20  to  40  plants  to  maturity. 


Fig.  66.  Older  seedlings  of  O. 
Lamarckiana  (L)  and  O.  gi^as 
(G).    c,  cotyledons,  red.  to  "A- 


Oenothera  Riihrincrvis.  Z27 

0.  gigas  has  appeared  twice  again,  but  not  directly 
from  O.  Lamar ckiana.  It  appeared  once  in  1898  from 
the  seeds  of  a  plant  of  O.  sublinearis  which  had  itself 
arisen  from  the  Lamarckiana-iam'ily.  It  appeared  again 
in  1899  from  a  cross  made  between  0.  lata  and  O.  Jiir- 
tella,  a  new  species  which  did  not  arise  from  my  mutating 
families  but  turned  up  among  the  seeds  which  I  had 
bought. 

I  succeeded  in  getting  the  first  of  these  ^z^a^-plants 
to  flower,  but  it  was  annual  and  did  not  flower  till  the 
beginning  of  October,  too  late  for  the  seed  to  ripen. 
I  therefore  compared  the  plant  very  carefully  with  the 
other  plants  of  that  species  which  I  had  growing  at  that 
time,  and  which  were  raised  from  gigas-SQeds;  it  agreed 
with  them  in  all  essentials. 

The  plant  which  mutated  from  0.  lata  died  as  a 
rosette  and  never  developed  a  stem. 

§    13.     OENOTHERA   RUBRINERVIS. 

This  form  unlike  Oenothera  gigas,  is  one  of  the  com- 
monest of  my  new  species.  It  has  arisen,  altogether, 
66  times  from  O.  Lamarckiana  or  from  other  families 
or  cultures.  It  is  hardly  necessary  to  state  that  among 
the  ancestors  of  these  mutants,  as  far  as  I  have  had  them 
under  observation,  there  have  been  no  examples  of  riibri- 
nervis.  And,  as  the  genealogical  tables  given  above 
show,  most  of  the  mutations  arose  in  families  which  had 
been  under  observation  for  many  generations. 

The  66  mutated  plants  belonged  to  a  single  type. 
They  did  not  differ  more  from  each  other  than  the 
members  of  a  culture  raised  from  the  seeds  of  a  single 
one  of  them.     Each  of  the  characters,  which  have  al- 


328   Origin  of  Each  Species  Considered  Separately. 

ready  been  briefly  described  on  p.  230  and  will  be  treated 
of  in  detail  shortly,  was  present  on  every  individual 
plant;  and,  as  far  as  investigated,  the  characters  did. not 
differ  from  plant  to  plant. 

Once  the  young  rosette  is  recognized  its  future  pecu- 
liarities can  be  predicted,  as  in  the  example  of  the  muta- 
tion of  which  Fig.  48  is  a  photograph,  which  was  also 
photographed  again  when  it  was  in  flower  (Fig.  49) 
(See  pp.  280  and  282).  I  have  often  planted  the  mutants 
singly  or  in  groups  so  soon  as  I  have  recognized  them 
in  order  to  be  able  to  follow  their  further  development 
during  the  course  of  the  summer. 

It  is  very  important  to  note  that  the  various  char- 
acters, the  red  coloring,  the  brittleness,  the  narrow  leaves, 
the  hairy  appearance,  and  so  forth,  have  never  appeared 
separately.  It  is  obviously  out  of  the  question  that  this 
association  can  be  ascribed  to  chance,  seeing  that  it  has 
occurred  in  66  cases.  There  can  be  no  doubt  that  there 
is  some  sort  of  a  connection  between  them. 

This  conclusion  receives  strong  support  from  the 
fact  that  even  in  the  oft"spring  of  crosses  the  ruhrinervis 
characters  remain  associated,  as  I  have  observed  in  numer- 
ous cases.  And  exactly  the  same  is  true  not  only  of  the 
newly  arisen  mutations  but  of  the  offspring  of  crosses 
made  with  them.  Every  species  has  its  "type"  according 
to  which  its  whole  nature  is  altered;  this  ''type"  affects 
its  whole  organization  in  such  a  way  that  hardly  a  char- 
acter or  an  organ  is  untouched  by  it. 

This  hidden  connection  between  characters  which  are 
invariably  associated  together  needs  an  explanation.  Two 
possibilities  present  themselves.  First,  it  is  conceivable 
that  all  these  visible  characters  are  only  expressions  of  a 
single  change,  and  that  a  mutation  is  brought  about  by 


Oenothera  Rubrinervis. 


329 


the  appearance  of  a  single  new  elementary  character. 
On  the  other  hand  it  might  be  supposed  that  in  mutation 
the  elements  of  the  species  are  changed  by  groups.    There 


Fig.  67.  Oenothera  rubrinervis.  An  entire  flowering  plant, 
1900.  Fourth  generation  of  a  rubrinervis-iamily  which 
arose  in  1895  from  seeds  of  O.  Lamarckiana  as  shown  in 
the  pedigree  on  page  262,  that  is  to  say  from  the  second 
generation  of  Lamarckiana  in  that  culture. 

is  abundant  a  priori  and  a  posteriori  evidence  for  the 
view  that  the  characters  of  plants  are  often  associated 
in  groups  in  such  a  way  that  whole  series  of  them  react 


330   Origin  of  Each  Species  Considered  Separately. 

as  one  unit  to  external  stimuli,  and  also  that  in  hybridi- 
zation and  other  breeding  experiments  these  characters 
behave  as  if  combined  into  inseparable  groups.^ 

If  we  should  ultimately  succeed  in  splitting  up  the 
group  of  riihrinervis-z\'\2ir2iQ.tQvs  into  its  component  units 
we  should  of  course  demonstrate  its  compound  nature. 
But  until  this  has  been  done  it  seems  to  me  both  simpler, 
and  better  in  accord  with  the  facts,  to  adopt  the  view 
that  the  sum  total  of  the  characters  is  the  expression  of 
a  single  elementary  "unit." 

How  it  comes  about  that  this  ''unit"  can  make  the 
walls  of  the  bast-fibres  thin,  the  leaves  narrow  and  gray- 
green,  the  veins  and  fruits  reddish,  is  a  question  which 
cannot  be  answered  at  present.  But  chemical  combina- 
tions also  possess  many  attributes  the  interdependence 
of  which  one  is  far  from  being  always  able  to  explain. 

I  shall  not  go  further  into  this  question  now ;  but 
before  I  leave  it  I  wish  to  insist  on  the  fact  that  the 
whole  so-called  ''habit"  of  a  species  can  be  so  much 
altered  by  a  mutation  that,  during  its  whole  life  and  in 
every  organ  it  differs  from  the  species  from  which  it 
arose. 

If  we  refer  to  the  pedigrees  and  tables  of  mutations 
given  in  sections  1-8  we  shall  find  the  cases  of  O.  rubri- 
nerz'is  which  are  recorded  in  the  following  table.  In  it 
we  see  that  one  0.  rithrinervis  occurs  in  about  every 
1000  seedlings. 

Besides  this,  O.  ruhrinervis  arose  twelve  times  in 
other  cultures  which  were  either  lateral  branches  of  the 
pedigrees  referred  to,  or  had  arisen  from  crosses.  I  have 
summarized  these  in  Table  II. 

The  proportion  of  0.  ruhrinervis  to  the  whole  num- 

^  Intracellulore  Pangenesis,  pp.  21,  33,  ec.  • 


\ 


Oenothera  Rubrmervis. 


331 


ber  of  seedlings  will  be  seen  to  be  much  greater  than  in 
the  first  table.  It  amounts  here  to  about  6  per  thousand. 
But  it  must  be  mentioned  that  only  those  cases  are  in- 

INDIVIDUALS   OF   OENOTHERA   RUBRINERVIS   WHICH    HAVE 

ARISEN   BY   MUTATION. 
I 


SOURCE  YEAR 

^    T  u-  S  1890,  1895  ) 

(J.  I^amarcKtana      .     .     .     .  -j  loqc;    icqy  r 

A  branch  of  the  same  family     1895,  1896 

O.  laevifolia 1889,  1894 

O.lata 1900 

O,  oblonga 1897 

O.  Laniarckiana  X  O.  nanella      1897 
O.  lata  X  O.  naftella  .     .     .     1895,  1900 
O.  Lamarckiana  from  the  field       1889 


SEEDLINGS 
TOTAL      RUBRINERVIS 


33,800 

32 

10,000 

9 

4 

2,000 

3 

45 

1 

1,051 

2 

222 

2 

1 

Total    54 


INDIVIDUALS   OF   OENOTHERA    RUBRINERVIS    WHICH    HAVE 

ARISEN   BY   MUTATION. 
II 


SOURCE 

O,  Lamarckiana,  a  biennial  culture 
O.  lata  which  mutated  from  O 

Lam.,  first  generation    . 
O.  lata  X  O.  Lamarckiana 
O.  lata  X  O.  brevistylis    . 
O.  nanella  X  O.  brevistylis 
O.  scintillans  X  O.  nanella 
O.  Laynarckiana  arisen  from  the 

cross  O.  Lam.  X  O.  scintillans 


eluded  in  which  the  species  in  question  actually  occurred 
and  that  a  figure  which  properly  represents  the  proportion 
of  0.  rubrinerz'is  cannot  be  obtained  without  including 


YEAR 

SEEDLINGS 

TOTAL 

RUBRINERVIS 

1897 

164 

2 

1896 

326 

4 

598,  1900 

750 

2 

1896 

266 

1 

1895 

270 

1 

1898 

95 

1 

1900 

80 

1 

Total 

1951 

12 

V 


2>2>2   Origin  of  Each  Species  Considered  Separately. 

all  the  cultures  irrespective  of  whether  they  contained  it 
or  not.  On  tlie  latter  estimate  the  number  would  prob- 
ably sink  to  0.1  %,  if  not  lower. 

It  has  already  been  stated  that  0.  nibrinervis  can  be 
recognized  as  quite  a  young  plant.  Pans  or  boxes  con- 
taining nothing  but  0.  nibrinervis  can  be  identified  very 

A' 

.A 


G'P^ 


Fig.  68.  Seedlings  of  Oenothera  ruhrinervis  at  various 
ages ;  c,  the  cotyledons ;  A,  with  the  first  two  leaves  at 
the  beginning  of  May;  A' ,  the  natural  size  of  the  same. 
B,  14  days  older.  C ,  Rosette,  towards  the  end  of  June, 
just  before  transplanting,  from  a  pan  in  which  the  seed- 
lings were  growing  very  close.  Compare  Fig.  64,  p.  325 
and  Figs.  65  and  66,  p.  326. 


early,  a  good  deal  earlier  than  mutants  standing  amongst 
other  species  (Fig.  48  on  page  280).  But  in  these  the 
narrow  leaves  with  their  red  veins  and  gray  felt-like 
surface,  the  almost  complete  absence  of  crumples  and  the 
brittleness  especially  of  the  stalk,  clearly  distinguish  this 
form  from  0.  Lamar ckiana  and  the  rest,      (Compare 


Oenothera  Riibrinervis.  333 

Fig.  68  with  the  similar  ones  of  O.  Lamarckiana  Figs. 
64-66). 

The  narrow  form  of  the  leaves  is  well  brought  out 
in  Figs.  52  and  54.  The  older  the  plants  become  the 
greater  becomes  the  difference  and  the  more  certain  the 
diagnosis.  As  a  rule  I  have  removed  the  mutants  at  an 
age  when  they  have  about  twice  as  many  leaves  as  the 
rosette  figured  at  Fig.  68  C.  The  plants  shown  there 
are,  of  course,  not  mutants  but  are  raised  from  seeds 
of  0.  ruhrinervis  and  selected  from  the  crop  as  the  most 
typical  examples  of  that  species. 

As  the  plants  get  older  the  veins  of  the  leaves  lose 
their  pale  red  color  more  or  less ;  but  this  depends  on 
how  they  are  grown  and  on  the  amount  of  sun  they 
get.  On  the  other  hand,  with  age  the  red  pigment  be- 
comes more  evident  in  the  inflorescences,  the  flowers  and 
the  unripe  fruits,  thereby  contributing  greatly  to  the 
characteristic  look  of  the  species.  The  young  internodes 
of  the  stem  are  suffused  with  red,  and  this  color  is  par- 
ticularly pronounced  in  the  swollen  bases  of  the  larger 
hairs.  The  tips  of  the  calyx  are  spotted  with  red  and  the 
flowers  become  much  darker  when  they  wither  than  those 
of  O.  Lamarckiana,  reminding  one  of  those  species  the 
leaves  of  which  become  red  when  they  wither,  such  as 
O.  stricta,  0.  missouriensis,  and  particularly  the  white 
O.  acanlis.  The  fruits  are  marked  with  four  broad, 
dark  red,  longitudinal  stripes,  one  along  the  middle  of 
each  valve.  But  in  this  case  the  redness  varies  accord- 
ing to  the  position  of  the  fruits  and  from  individual  to 
individual  within  apparently  wide  limits;  sometimes,  in- 
deed, the  stripes  are  very  difficult  to  find. 

This  red  pigment  occurs  also  in  0.  Lamarckiana  and 
particularly  in  the  unripe  fruits ;  but  very  indistinctly : 


334   Origin  of  Each  Species  Considered  Separately, 


whilst  in  0.  nihrinervis  the  red  stripes  are  handsome  and 
striking. 

To  turn  now  to  the  general  structure  of  the  plant; 
it  has  a  greater  tendency  to  develop  lateral  branches 
from  the  main  stem  and,  in  connection  with  this  fact 
doubtless,  fewer  from  the  rosette  (compare  Figs,  49  and 
67  with  Fig.  55).  But  this  feature  is  greatly  affected 
by  the  manner  of  cultivation. 


Fig.  69.  Oenothera  ruhrinervis.  A,  Transverse  section  of 
the  stem  ;  m.  pith  ;  p,  inner  phloem ;  h,  wood ;  b,  bast  bun- 
dles between  the  outer  phloem  and  the  bark ;  B,  part  of 
such  a  bundle  highly  magnified;  C,  the  same  of  O.  La- 
mar ckiana. 

This  form  can  be  distinguished  at  some  little  distance, 
from  the  common  Evening  Primrose  by  the  general  habit 
of  its  inflorescence  and  flowers ;  but  it  is  very  difhcult  to 
find  differentiating  characters  which  can  be  described. 
Plate  I  might,  if  it  did  not  lack  red  pigment,  pass  as  well 
for  a  ruhrinervis  as  a  Lamarckiana  (see  Fig.  43,  p.  232). 

The  whitish  gray  color,  which  is  seen  in  a  more  pro- 
nounced state  in  O.  alhida,  is  not  really  due,  as  it  appears 
to  be,  to  the  greater  hairiness  of  the  plant ;  but  is  brought 
about  by  the  swollen  surfaces  of  the  cells  of  the  epidermis 


Oenothera  Ruhrinervis.  335 

which  have  not  grown  out  in  the  form  of  hairs.  This 
swelhng  is  very  shght  in  0.  Lamarckiana. 

It  has  already  been  stated  in  §  3  of  this  Part  that 
one  of  the  most  characteristic  features  of  0.  ruhrinervis 
is  the  brittleness  of  its  stem.  The  latter  as  well  as  the 
petioles  of  the  leaves  are  very  fragile  and  break  off  at 
the  merest  touch.  The  cause  of  this  is  the  weak  develop- 
ment of  the  hard  bast.  It  is  only  biennial  plants  or  very 
strong  annual  ones  that  break  in  late  autumn  in  the  way 
that  0.  Lamarckiana  does  when  the  hard  bast  is  torn. 

A  transverse  section^  of  the  stem  of  a  plant  about  a 
meter  high,  taken  in  August,  shows  the  bast-fibres  in  a 
discontinuous  ring  around  the  outer  side  of  the  wood 
and  inside  the  bark,  as  shown  in  Fig.  69  A.  If  we  com- 
pare such  a  section  with  a  similar  one  of  0.  Lamarckiana 
we  do  not  at  first  see  any  difference.  In  both  plants  the 
sclerenchymatous  strands  are  about  equally  developed. 
But  if  we  examine  a  single  strand  under  a  higher  power 
we  find  that  in  O.  Lamarckiana  it  is  better  developed  in 
the  radial  and  less  so  in  the  tangential  direction  than  in 
0.  ruhrinervis.  The  most  important  difference  however 
lies  in  the  thickness  of  the  walls  of  the  individual  cells 
which,  as  Figs.  69  B  and  C  show,  are  about  half  as  thick 
in  O.  ruhrinervis  as  they  are  in  the  parent  species. 

There  is  great  difference  between  individuals  in  re- 
spect to  this  character  depending  on  whether  they  have 
plenty  of  room  to  grow  in,  or  are  crowded  together;  or 
whether  they  are  sown  early  or  late.  Weak  plants  never 
entirely  lack  the  bundles,  though  the  individual  cells  of  the 
bundles  are  fewer  and  more  tangentially  arranged.  They 
often  retain  these  characters  until  they  ripen  their  fruits. 

^  For  the  general  anatomy  of  the  stem  see  Francis  Ramsay,  On 
the  Stem  Anatomy  of  Certain  Onagraceae,  Minnesota  Botanical  Stud- 
ies, Bull.  No.  9,  Nov.  1896,  p.  674. 


336   Origin  of  Each  Species  Considered  Separately. 


In  late  autumn  there  appears  on  the  inner  side  of  the 
sclerenchym  ring  a  thin  layer  of  cork  which  must  of 
course  have  been  laid  down  much  earlier  and  possibly 

stands  in  some  causal  re- 
lation to  the  external 
characters  of  the  plant. 
This  species  is  char- 
acterized by  an  apparent 
inability  to  stretch  its 
stem  —  so  to  speak  — 
which  is  particularly  no- 
ticeable in  weak  plants. 
This  character  is,  in  all 
probability,  due  to  the 
weakness  of  the  bast- 
fibres  we  have  just  de- 
scribed. Fig.  70  repre- 
sents a  young  plant 
grown  in  a  pot,  about  the 
beginning  of  July,  and 
illustrates  this  feature 
very  well.  The  stem  is 
not  straight  but  bent  in 
a  zig-zag  fashion;  in 
such  a  way  that  the 
bends  occur  at  the  nodes 
and  the  leaves  are  in- 
serted in  their  outer  con- 
vex sides.  These  bends 
do  not  straighten  out 
with  subsequent  growth ;  in  fact  they  are  often  even  more 
pronounced  on  the  fruiting  plants.  The  stronger  the 
stem  is,  the  less  is  this  character  developed;  but  I  have, 


Fig.  70.  Oenothera  rnhrinervis. — 
Young  annual  plant,  30  cm.  high, 
about  V3  natural  size.  To  show  the 
zigzag  course  of  the  brittle  stem. 


Oenothera  Ohlonga.  ZZ7 

nevertheless,  found  it  on  perfectly  healthy  annual  plants 
whose  main  stems  have  been  heavily  laden  with  fruit. 

I  have  already  recorded  experiments  on  the  con- 
stancy of  O.  rtihrinervis  §  3  (p.  232)  and  §  5  (p.  274). 
These  experiments  show  that  plants  raised  from  the  seed 
of  mutated  individuals  are  exactly  like  their  parents,  and 
that  the  characters  we  have  described  for  the  parents 
reappear  in  the  children  in  exactly  the  same  degree.  O. 
ruhrinervis  itself  is  very  slightly  mutable  and  seems  to 
confine  itself  to  throwing  off  lata  and  leptocarpa,  as  al- 
ready shown  on  page  273. 


§  14.    OENOTHERA  OBLONGA. 
(Plate  VI.) 

0.  ohlonga  has  arisen  much  more  frequently  than 
O.  rnbrinerz'is  both  from  0.  Laniarckiana  itself  and 
other  species  and  crosses.  I  have  seen  it  arise  altogether 
about  700  times  from  one  form  or  another  of  known 
and  pure  ancestry.  The  various  cultures  in  which  it 
arose  comprised  about  70,000  seedlings.  We  might 
therefore  almost  speak  of  coefficients  of  mutation ;  which 
in  the  case  of  this  species  would  be  about  1  '^/c,  in  the 
case  of  O.  ruhrinervis  0.1  %  and  in  that  of  0.  gigas 
0.01  %. 

What  is  the  cause  of  these  differences?  They  cannot 
be  ascribed  to  defective  observation.  I  first  saw  0.  oh- 
longa in  1895  when  my  cultures  were  very  extensive;  in 
previous  years  they  were  probably  there,  but  escaped  my 
observation.  Their  young  rosettes  are  as  easy  to  recog- 
nize as  those  of  O  ruhrinervis;  and  often  somewhat 
earlier,  as  rosettes  with  six  leaves.     But  evidently  this 


338   Origin  of  Each  Species  Considered  Separately. 


fact  cannot  explain  the  difference   in  the  mutation-co- 
efficients. 


Fig.  71.  Oenothera  oblonga.  Upper  and  middle  section 
of  a  plant  in  September  to  show  the  peculiar  type  of 
branching  with  rosette-like  lateral  branches,  (Compare 
Fig.  67  on  page  329.)  Reduced  to  Vs  natural  size.  The 
smaller  figures  similarly  reduced,  a,  a  flower ;  a  petal  is 
removed  and  shown  separately  at  b;  c,  a  flower  without 
the  corolla,  showing  the  stamens  which  are  bent  down- 
wards at  the  base  but  upwards  again  towards  their  tips, 
and  the  style  with  the  four  stigmata;  d,  ripe  fruits;  e, 
one  of  their  bracts. 

These  differences  in  the  "mutation  coefficients"  hold 
good,  too,  of  the  individual  families.  Not  exactly  of 
course,  but  to  such  an  extent  that  in  large  sowings  the 


Oenothe?'a  Oblonga.  339 

ohlonga  mutants  are  almost  always  considerably  more 
numerous  than  the  ruhrinervis  ones.  The  observations 
extend  over  six  years  (1895-1900),  which  is  probably 
only  a  small  section  of  the  whole  mutation  period.  Never- 
theless, the  evidence  seems  to  justify  the  conclusion  that 
the  various  new  species  arise  from  the  parent  form,  at 
any  rate  for  a  certain  period,  in  definite  and  constant 
proportions  which  vary  from  species  to  species. 

This  consideration  seems  to  me  to  lead  to  two  im- 
portant points.  First,  the  probability  that  0.  Lamarckiana 
is  able  to  produce  other  mutations  in  even  smaller  pro- 
portions, such  as  one  in  a  million;  in  which  case  there 
would  not  be  much  chance  of  their  appearing  in  my  cul- 
tures. In  other  words  if  one  could  make  the  whole  ex- 
periment ten  or  a  hundred  times  as  extensive,  one  would 
be  very  likely  to  get  more  mutations  and  amongst  them, 
possibly,  some  better  than  those  which  have  already  ap- 
peared. 0.  laevifoUa  and  0.  hrcvistylis  might  then  arise 
again. 

The  second  point  relates  to  the  causes  of  these  pro- 
portions. Is  it  possible  to  interfere  with  and  alter  the 
"mutation  coefficients"  ?  Is  there  any  hope  of  increasing 
the  proportion  of  the  rarer  species?^  And  when  a  method 
of  doing  this  will  be  invented  will  it  be  possible  to  obtain 
mutations  which  are  at  present  presumably  too  rare  to 
appear  ? 

An  experimental  study  of  the  process  of  mutation 
during  the  mutation  period  may  even  put  into  our  hands 
the  power  to  bring  about  the  inception  of  such  a  period ; 
or  in  other  words  the  power  to  make  an  immutable  spe- 
cies mutable. 

^  See  the  case  in  §  <  (on  page  264)  where,  as  a  result  of  defective 
germination  the  proportion  of  mutants  arose  to  40  %. 


340   Origin  of  Each  Species  Considered  Separately. 

But  let  us  return  to  the  figures  which  seem  to  justify 
these  hopes. 

I  shall  first  give  the  values  for  the  chief  families  and 
then  those  for  their  lateral  branches. 


INDIVIDUALS  OF  OENOTHERA  OBLONGA  WHICH   HAVE 

ARISEN   BY   MUTATION. 

I 

A.    FROM    0.    LAMARCKIANA. 

Main  family  .     .     .  1895  14,000  176  1.3 

...  1896  8,000  135  1.7 

A  collateral  family  1895  10,000  69  0.7 

Biennial  culture      .  1897  1,660  31  1.9 


Totals    33,660 

411 

1.2 

B.    FROM    0.    LATA. 

Lafa-fa.mi\y  .     , 

,     .     1900                  2,000 

7 

0.3 

Z.a/tz-cultures 

.     1895-1898            2,350 

28 

1.2 

Totals    4,350  35  0.8 

C.    FROM    O.    NANELLA. 

O.  nanella     .     .     .     1897  760  1  0.1 

Although  the  /a/a- family  of  1900  is  considerably  be- 
low the  average,  the  percentages  in  groups  A  and  B  con- 
form pretty  closely  to  a  general  proportion  of  about  1  %  ; 
whilst  the  figure  for  O.  nanella  affords  a  good  example 
of  the  rule  that  new  species  mutate  less  than  0.  La- 
marckiana  or  than  0/  lata  fertilized  with  Lamarckiana 
pollen. 

About  the  same  proportion  is  maintained  in  crosses. 
The  following  table  embodies  results  already  described, 
together  with  some  to  be  referred  to  later  on. 


Oenothera  Ohlonga.  341 


DATE 

TOTAL 

OBLONGA 

.   1897-1899 

8283 

38 

is      1898 

293 

4 

.   1895-1900 

1586 

14 

.   1895-1899 

498 

6 

1895 

127 

4 

.       1895 

1500 

4 

1898 

95 

3 

1896 

30 

2 

fis     1897 

200 

8 

Totals 

12,612 

83  —  0.7  % 

INDIVIDUALS    OF    OENOTHERA    OBLONGA    WHICH     HAVE 

ARISEN  BY  MUTATION. 

II 

FROM    CROSSES. 

SOURCE 

O.  Lamarckiana  X  O  nanella 
O.  Lamarckiana  X  O.  brevistyli 
O.  lata  X  O.  nanella    ..     .     . 
O.  lata  X  O.  brevistylis     ■.     . 
O.  lata  X  O.  laevi folia      .     . 
O.  rubri7iervis  X  O.  nanella- 
O.  scintillans  X  O.  nanella  , 
O.  Lafnarckiana  X  O.  bietmis 
O.  Lamarckiana  X  O.  suaveolens 


To  obtain  the  above  figures  I  have  sometimes  re- 
corded the  seedhngs  when  they  had  from  6  to  8  leaves 
but  at  other  times  later,  according  to  the  different  years 
and  various  other  circumstances.  In  many  cases  I  have 
transplanted  them  in  order  to  observe  them  during  the 
whole  summer.  Fig.  72  gives  an  idea  of  the  stage  at 
which  the  seedlings  were  recorded,  and  may  be  com- 
pared with  the  parallel  figures  for  the  /a^a-families  (Plate 
IV  and  Fig.  48,  p.  280).  We  are  concerned  in  Fig.  72 
with  a  culture  of  O.  Lamarckiana  which  was  sown  on  the 
14th  of  March  1900  and  transplanted  into  wooden  boxes 
on  the  14th  of  April.  The  seeds  had  been  harvested  in 
1895  from  three  plants  enclosed  in  parchment  bags  to 
insure  pure  self-fertilization.  Of  the  188  seedlings  raised, 
4  were  mutations  of  which  two  were  albida  and  two  ob- 
longa.  By  a  lucky  chance  an  example  of  each  of  the 
new  forms  stood  quite  close  together;  so  that  I  was  able 
to  include  them  in  the  same  photograph  (Fig.  72).    The 


342   Origin  of  Each  Species  Considered  Separately. 

plants  are  arranged  in  rows  in  the  boxes :  0.  albida  can 
be  recognized  at  once  in  the  middle  of  the  figure  by  its 
small  size;  just  underneath  it  is  the  0.  ohlonga  which 
can  hardly  be  distinguished  in  the  figure.  I  transplanted 
these  two  plants  on  to  a  separate  bed  to  watch  their  further 
development.  They  grew  up  to  strong  rosettes  which 
exhibited  all  the  characters  of  the  species  to  which  they 


Fig.  72.  A  mutation  in  a  culture  of  O.  Lamarckiana.  Ori- 
gin of  O.  albida  and  O.  ohlonga.  From  a  photograph 
taken  at  the  end  of  May  1900.  In  the  middle  of  the 
middle  row  is  the  little  O.  albida ;  in  the  middle  of  the 
lower  row  O.  ohlonga.  The  other  seedlings  are  O.  La- 
marckiana ;  Vs  natural  size. 

belonged,  clearly  and  beautifully;  but  were  destroyed  in 
the  autumn  by  the  caterpillars  of  Agrotis  segetum. 

Seedlings  of  even  less  than  6  or  8  leaves  can  often 
be  recognized ;  but  it  is  very  difficult  to  describe  the 
characters  which  render  their  identification  possible.  In 
Fig.  73  at  A  3.  very  young  seedling  is  shown  with  its 


Oenothera  Oblonga. 


343 


first  two  leaves,  and  at  5  a  rosette  two  months  old.  These 
are  not  mutants  but  plants  grown  from  the  seed  of  self- 
fertilized  oblonga.  These  cultures  came  quite  true  to 
seed  and  exhibited  a  high  degree  of  uniformity.  The 
first  two  leaves,  after  the  cotyledonary  ones,  are  broad 
and  with  broad  bases,  markedly  broader  than  those  of 
O.  Lamarckiana  at  the  corresponding  age  (Fig.  65  L,  p. 
326).  This  can  be  seen  in  Fig.  72>  A  and  5  at  1  and  2 
as  well  as  in  Fig.  72.  There  soon  follow  narrower  leaves 
but  the  rate  at  which  this  decrease  in  breadth  takes  place 
is  not  constant.  Fig.  72)  B  is  more  typical  in  this  respect 
than  the  O.  oblonga  of  Fig.  72,  but  the  remaining  seedlings 


Fig.  yz-  Seedlings  of  Oenothera  oblonga.  A,  a  few  weeks 
old,  magnified  (2.5/1).  B,  two  months  old,  'A  natural 
size,  c,  cotyledonary  leaves.  In  B  the  leaves  are  marked 
in  the  order  in  which  they  appeared. 

in  the  same  box  behaved  essentially  in  the  same  manner. 
I  photographed  many  of  them  at  the  time,  but  do  not 
think  it  worth  while  to  reproduce  the  others  as  well. 

As  the  plants  grow  their  characters  become  more 
pronounced,  the  leaves  longer  and  narrower,  the  veins 
broader,  paler  and  more  prominent.  In  the  third  month 
growth  takes  place  much  faster,  or  at  any  rate  produces 
a  more  noticeable  increase  than  in  the  first  two.  At  the 
end  of  that  period  the  rosettes  possess  many  leaves  and 
are  very  strong  and  ready  for  the  development  of  the 
stem  (Fig.  74).     If  they  do  not  do  this  they  grow  to  a 


344   Origin  of  Each  Species  Considered  Separately. 

considerably  greater  size  during  the  summer  and  increase 
the  number  of  their  leaves  without,  however,  altering 
their  general  appearance.  A  very  typical  leaf  with  its 
venation  will  be  found  in  Fig.  54  (See  p.  295). 

If  the  rosettes  develop  stems  in  June  and  July  they 
flower  that  summer.  Such  plants  are  very  uniform  in 
character,  they  are  slender  and  yet  firm,  and  branched 
either  very  little  or  not  at  all.  Hardly  any  differences 
were  discernible  between  200  flowering  plants  growing 


Fig.   74,     Oenothera   ohlonga.     A   rosette   with    radical 
leaves  at  the  end  of  June. 

together.  The  tallest  plant  began  to  flower  when  it  was 
60  cm.  high,  and  flowered  till  the  end  of  September  when 
it  had  attained  a  height  of  one  meter.  It  had  a  single 
lateral  branch  only  10  cm.  long  and  with  only  two  flow- 
ers on  it ;  all  that  there  w^as  in  the  way  of  lateral  branches 
besides  this  was  a  series  of  rosette-like  offshoots  from  the 
axils  of  the  leaves  along  the  middle  region  of  the  stem. 
The  result  of  this  is  the  very  characteristic  ensemble 


Oenothera  Oblonga.  345 

(Fig.  71  B)  which  is  always  found  in  all  the  plants  of 
this  species.  The  culture  in  question  did  not  contain 
a  single  plant  bearing  flowers  on  a  lateral  stem,  with  the 
exception  of  the  plant  referred  to. 

At  the  time  when  the  plant  is  about  to  flower  (Fig. 
44,  p.  233)  the  flowering  spike  is  still  densely  clothed 
with  leaves.  Higher  up,  the  bracts  become  shorter.  The 
fruits  likewise  do  not  attain  the  size  of  those  of  0.  La- 
marckiana ;  and  we  get  in  this  way  another  very  striking 
character  which  can  be  well  seen  by  comparing  Plate  VI 
with  Plate  I.  The  ripe  fruits  hardly  attain  a  third  of 
the  length  of  those  of  O.  Lamarckiana.  As  a  result  of 
this,  the  seeds  are  often  bad  and  developed  in  very  small 
quantity  so  that  all  that  can  be  hoped  for  is  a  very  meagre 
harvest  at  the  best. 

Biennial  plants  are  much  better  in  this  respect;  they 
are  more  robust  and  bear  numerous,  strong,  though  small, 
fruits  which  contain  an  abundance  of  seed.  These  fruits 
are  not  much  longer  than  those  of  the  annual  plants  but 
much  stouter,  rather  like  those  of  0.  lata. 

When  grown  under  more  favorable  conditions  the 
annual  as  well  as  the  biennial  plants  develop  a  certain 
number  of  lateral  stems  from  the  axils  of  the  radical 
leaves,  such  as  have  already  been  figured  in  the  case  of 
a  mutation  from  the  /a/a-family  (Fig.  50,  p.  284).  But, 
even  so,  the  main  stem  itself  remains  unbranched,  a  pecu- 
liarity which  can  best  be  seen  by  comparing  such  a  plant 
with  O.  nihrinervis  (Fig.  49,  p.  282). 

There  is  not  much  to  be  said  about  the  flowers  and 
buds  of  O.  oblonga  (See  Plate  VI).  They  have  the 
same  form  as  those  of  the  parent  species;  but  in  cor- 
respondence with  the  greater  delicacy  of  the  whole  plant 
thev  are  a  trifle  smaller. 


346   Origin  of  Each  Species  Considered  Separately. 

I  first  harvested  the  seed  of  O.  ohlonga  in  1895;  but 
as  the  plants  had  flowered  too  late  they  had  not  been 
artificially  fertilized  and  the  seed  only  gave  quite  a  small 
percentage  of  ohlonga.  But  in  1896  I  harvested  self- 
fertilized  seed  partly  from  annual  and  partly  from  bi- 
ennial plants.  The  plants  were  all  mutants,  that  is,  had 
all  arisen  from  0.  Lamarckiana  of  pure  strain,  in  fact 
from  the  main  line  of  descent  of  the  Lamarckiana-iamily 
itself  (See  the  genealogical  table  on  p.  224).  The  bi- 
ennial plants  had  therefore  three  generations  of  pure 
Lamarckiana  behind  them;  and  the  annual  ones  four. 
There  were  seven  plants  in  the  first  and  twelve  in  the 
second  group. 

I  sowed  the  seed  in  the  middle  of  April  1897,  and  as 
the  seed  had  not  been  sown  too  thick  the  seedlings  dis- 
played their  characteristic  features  as  early  as  the  middle 
of  June,  in  the  seed  pans.  The  leaves  with  the  exception 
of  the  first  two  broad  ones  (p.  342)  were  narrow  and 
had  long  petioles;  and  exhibited  the  characteristic  broad 
pale  midveins.  A  comparison  with  cultures  of  the  or- 
dinary Evening  Primrose  at  the  same  stage  of  develop- 
ment made  it  certain  at  once  that  there  were  no  La- 
marckianas  among  the  ohlonga  crops.  The  sowings  were 
perfectly  true,  with  the  exception  of  four  seedlings  one 
of  which  became  a  ruhrinervis,  one  an  elliptica  and  two 
alhida  (p.  297).  Besides  this,  one  plant  had  a  pitcher 
shaped  leaf.  I  counted  the  seedlings  for  17  out  of  the 
19  seed  parents  separately;  and,  as  I  have  already  stated 
above  (p.  235),  they  were  all,  with  the  exceptions  named, 
ohlongas  (1683  and  64;  together,  1747  plants). 

In  the  same  year  I  sowed  the  self -fertilized  seed  of 
three  other  mutants  which  had  arisen,  in  order  to  find 
out  whether  the  difference  in  their  origin  would  cause 


Oenothera  Ohlonga.  347 

them  to  differ  from  the  other  mutants  in  the  matter  of 
constancy.  I  will  describe  the  ancestry  of  the  three  plants 
separately. 

The    first   arose    from   the   laevifolia-i^xmly,    whose 
pedigree  has  been  given  on  p.  273,  in  the  following  way : 

1895-1896  O.  oblonga 

I 
1894  O.  rubrinervis 

I 
1893  O.  rubrinervis y  5th  gen.,  X  O.  natiella,  4th  gen. 

Similar  intermediate 
generations 

1889  O.  rubrinervis  O.  fianella 


1888  O.  Lamarckiafia 

I 
1886-1887  O.  laevifolia  from  Hilversum 

The  first  three  generations  in  this  pedigree  as  well 
as  the  rubrinervis  of  1893  have  already  been  referred 
to  on  p.  273.  The  0.  nanella  w^as  biennial  in  1889,  but 
since  then  has  been  annual.  In  the  summer  of  1893  I 
pollinated  some  castrated  flowers  of  O.  rubrinervis  with 
the  pollen  of  0.  nanella;  in  1894  I  obtained  from  these 
seeds  some  ordinary  rubrinervis  plants,  which  were  fer- 
tilized with  their  own  pollen  and  produced  mainly  O. 
rubrinervis.  But  amongst  them  were  four  oblonga  (p. 
341 )  of  which  I  managed  to  bring  one  safely  through  the 
winter  as  a  rosette.  It  flowered  in  1896  in  a  parchment 
bag;  16  seedlings  were  raised  from  it  and  were  subse- 
quently transplanted  into  pots ;  they  were  all  oblonga. 

The  second  oblong a-muidLni  arose  likewise  from  the 
laevifolia-fsimWy.  It  arose  from  a  self- fertilized  La- 
marckiana  plant,  in  the  main  line  of  descent  in  1894,  a 
plant  which  had  itself  therefore  arisen  partly  from  laevi- 
folia and  partly  from  Lamarckiana  stock,  but  which,  at 


348   Origin  of  Each  Species  Considered  Separately. 

least  so  far  back  as  1896,  had  ancestors  of  no  other  type. 
This  ohlonga  belonged  to  the  9th  generation  of  the  fam- 
ily. It  was  biennial ;  was  self-fertilized  and  gave  rise  to 
297  seedlings.  Amongst  these  I  found  a  single  0.  albida ; 
all  the  rest  were  0.  ohlonga. 

The  third  plant  belonged  to  a  lateral  branch  of  the 
Lamarckiana-family.  In  the  pedigree  on  p.  224  five  lata 
plants  will  be  found  for  1888.  One  of  them  which  had 
a  fine  ascidia  flowered  in  1889;  but  its  seeds  were  not 
sown  till  1894.  This  second  generation  was  annual  and 
left  to  be  pollinated  by  insects.  In  1895  I  raised  from  its 
seeds  128  Lainarckiana,  18  lata,  3  nanella  and  10  oh- 
longa. Of  the  latter  one  plant  flowered  in  its  second 
year,  i.  e.,  in  1896,  in  a  parchment  bag.  Of  its  seeds 
91  germinated  and  gave  rise  solely  to  ohlonga  plants. 

These  experiments  show  that  the  constancy  of  O. 
ohlonga,  when  it  arises  as  a  mutant,  is  independent  of 
the  character  of  its  ancestors.  These  may  ht  Lamarckiana, 
laevifolia,  rnhrinervis,  nanella,  pure  or  hybrid,  but  the 
ohlonga  which  arises  from  them  is  always  pure  from  the 
first  generation;  except,  of  course,  that  it  has  inherited 
the  mutability  of  its  parent  and  has  the  capacity  for 
giving  rise  to  other  types  (alhida,  rnhrinervis). 

The  total  number  of  plants  recorded  in  the  experi- 
ments of  this  year  is  1747+16  +  297  +  91=2151. 
I  have  sown  seeds  of  the  same  mother  plants  in  subse- 
quent years,  in  1899  and  1900  and  always  with  the  same 
result.  I  have  so  far  not  harvested  any  seed  of  the 
second  generation  because  although  the  plants  flowered 
freely  they  were  all  annual  and  so  produced  only  imper- 
fect fruits. 


Oenothera  Alhida.  349 

§  15.   OENOTHERA  ALBIDA. 
(Plates  III  and  IV.) 

A  beautiful  but  delicate  species  which  is  very  slow  in 
growing  as  a  seedling  and  is  for  that  reason  very  easily 
recognized.  See  Fig.  48  on  p.  280  and  Fig.  72  on  p.  342. 
These  weak  plants  are  at  a  great  disadvantage  when 
growing  among  the  much  stronger  seedlings  of  the  parent 
type;  and  it  is  only  very  rarely  that  I  succeeded  in 
getting  them  to  flower. 

It  was  in  1895  (as  has  already  been  stated  in  §  3, 
p.  229)  that  I  first  succeeded  in  getting  a  rosette  to  sur- 


Fig.  75.    Oenothera  alhida.     Young  seedlings;  A,  with 
the  first  two  leaves ;  B,  two  months  old. 

vive  the  winter ;  it  was  on  it  that  I  first  saw  the  flowers 
of  the  new  species,  but  I  got  no  seed  from  it.  Before 
this  I  had  seen  alhida  almost  every  year  and  in  no  in- 
considerable numbers,  but  thought  they  were  merely 
sickly  individuals  and  had  taken  no  further  account  of 
them.  That  is  why  the  records  that  follow  are  confined 
to  the  period  1895-1900. 

The  young  alhida  plants  are  so  delicate  that  it  is  only 
by  the  exercise  of  the  greatest  care  that  they  can  be  kept 


350   Origin  of  Each  Species  Considered  Separately. 


aliv'C.  I  never  found  them  at  Hilversum;  and  even  if 
they  had  ever  succeeded  in  germinating  there,  they  would 
most  certainly  have  perished  before  developing  a  stem. 
This  was  exactly  what  happened  in  my  experimental 
garden  from  the  time  my  experiments  began  until  1896. 
These  facts  moreover  show,  as  mentioned  above  (p.  229), 
that  my  first  alhida  mutants  could  not  have  had  similar 

individuals  in  their  an- 
cestry, neither  as  pollen 
parents  nor  as  seed  pa- 
rents. 

Even  when  0.  al- 
hida has  set  seed  the 
difficulty  of  getting  the 
seed  to  germinate  is 
considerable;  but  the 
attempt  to  keep  the 
young  plants  strong 
from  the  very  begin- 
ning has  succeeded. 
Some  of  them  always 
remain  weak  and  look 
just  like  the  young 
mutants,  others  bear 
broader  leaves  and 
gradually  grow  to  little 
rosettes  .which  are  apparently  just  as  strong  as  those  of 
O.  ohlonga  at  a  like  age  (see  Fig.  75).  Moreover  they 
differ  from  these  very  little  in  form  at  first  (Fig.  72)). 
But  their  color  is  always,  as  their  name  implies,  a  whitish 
gray.  For  the  first  six  weeks  of  their  existence  the 
leaves  of  these  two  species  are  about  the  same  breadth; 
those  of  O.  alhida  however  are  a  little  blunter  at  the 


Fig.    76.      Oenothera   alhida.     Young 
plant,  3V2  months  old. 


Oenothera  A  lb  id  a.  351 

tip.  During  the  growth  the  leaves  of  the  rosettes  in- 
crease in  breadth  as  a  rule  (Fig.  76)  whilst  those  of  the 
stem  become  narrow  again  (Fig.  54a  on  page  295). 

It  is  always  easy  to  recognize  albida  mutants  by  the 
characters  I  have  described.  I  have  cultivated  many  of 
them  beyond  this  stage,  especially  in  1895  and  the  fol- 
lowing years,  in  the  hope  of  getting  them  to  flower  and 
set  seed.  And  in  this  way  I  had  ample  opportunity  of 
testing  the  accuracy  of  my  diagnosis. 

The  ease  with  which  this  species  can  be  recognized 
as  quite  a  young  plant  makes  it  a  convenient  one  for  the 
study  of  the  relative  frequency  of  its  origin  from  O. 
Lamarckiana  and  other  species.  The  result  of  this  in- 
vestigation was  that  this  frequency,  this  coefficient  of 
mutation,  turned  out  to  be  very  different  in  different 
cases  and  to  be  subject  to  even  greater  fluctuations  than 
those  exhibited  by  the  three  species  described  above 
(0.01  %  for  O.  gigas,  0.1  fo  for  rnbrinervis  and  1  % 
for  oblonga). 

The  two  tables  that  follow  bring  this  out.  I  include 
in  them  figures  that  have  already  been  given  in  §§  2-5. 

INDIVIDUALS    OF    OENOTHERA    ALBIDA    WHICH    HAVE 

ARISEN   BY    MUTATION. 

I 


SOURCE  DATE  TOTAL 


SEEDLINGS 
ALBIDA       %  ALBIDA 


O.  Lamarckiana-isimWY    .  1895-1899  28,500  56  0.2 
O.   Lamarckiatia,    plants 

from  crosses    ....  1898  4,599  2  0.05 
A  lateral  branch   of    the 

Lamarckia7ia-isim\\Y     .  1895  10,000  255  2.5 

O.  lata 1900  2,000  42  2.1 

O.  lata 1896-1899  751  31  4.0 

O.  Lamarckiana,  biennial  1896  164  15  9.0 


1897 

1341 

1 

0.1 

1895-1900 

1535 

15 

1.0 

1900 

IS-U 

37 

2.0 

1900 

636 

2 

0.3 

1898 

95 

3 

3.0 

1900 

743 

13 

2.0 

352   Origin  of  Each  Species  Considered  Separately. 

The  proportion  of  albida  mutants  varies  between 
0.05  %  and  9  %. 

This  variabihty  is  also  exhibited  though  to  a  con- 
siderably less  extent  by  the  proportions  in  whicli  O.  al- 
bida occurs  among  the  offspring  of  various  crosses. 

INDIVIDUALS    OF    OENOTHERA    ALBIDA    WHICH    HAVE 

ARISEN   BY    MUTATION. 

II 

FROM  CROSSES. 
CROSS  DATE       TOTAL    O.  ALBIDA    %  ALBIDA 

O.  Lamarckiana  X  O.  nanella 
O.  lata  X  O.  nanella     . 
O.  lata  X  O.  rubrinervis  . 
O.  lata  X  O.  scintillans     . 
O.  scUitillans  X  O.  nanella 
O.  lata  X  O.  suaveolens    . 

The  mutants  obtained  in  these  two  series  of  experi- 
ments amounted  to  472  and  agreed  in  all  their  charac- 
ters so  far  as  these  could  be  investigated. 

Flowering  plants  of  0.  albida  can  be  distinguished 
from  all  other  subspecies  of  O.  Lamarckiana  and  from 
this  species  itself  just  as  easily  as  the  seedlings  and 
rosettes  can.  They  do  not  attain  even  in  late  autumn 
a  height  of  more  than  one  meter;  but  as  a  rule  they 
give  rise,  about  the  middle  of  their  stem  to  a  group  of 
flowering  branches,  in  the  same  way  that  O.  rubrinerzns 
does.  Their  leaves  are  narrow  (Fig.  SAA,  p.  295), 
pointed  and  very  uneven;  the  crumples  in  them  being 
more  numerous  and  more  pronounced  than  in  the  parent 
species  (Fig.  57,  transverse  section  of  a  leaf,  see  p.  310). 

The  flowers  are  always  somewhat  smaller  than  those 
of  Lamarckiana,  as  would  be  expected  from,  a  greater 
delicacy  of  the  species ;  moreover  they  have  a  tendency 


Oenothera  Leptocarpa.  353 

to  stand  more  upright,  and  not  to  open  so  wide  as  those 
of  the  parent  species  (compare  Plate  III  with  Plate  I). 
In  other  respects  they  have  the  same  structure,  and  the 
stigmas  stand  up  well  above  the  anthers.  The  color  of 
the  flower  is  a  paler  shade  of  yellow.  The  fruits  do  not 
attain  the  length  or  the  stoutness  of  those  of  0.  La- 
marckiana,  and  as  a  rule  set  little  seed. 

The  gray  color,  which,  like  that  of  0.  rttbrinervis  is 
not  due  to  increased  hirsuteness,  but  to  the  swelling 
of  the  outer  wall  of  the  ordinary  epidermis  cells,  ex- 
hibits a  high  degree  of  individual  variability,  sometimes 
indeed  to  such  an  extent  that  doubt  may  arise  as  to  the 
proper  diagnosis,  a  doubt  which  however  can  always 
be  dispelled  by  the  examination  of  later  stages. 


§  i6.    OENOTHERA  LEPTOCARPA. 

The  foregoing  examples  have  shown  us  that  muta- 
tions arise  from  Oenothera  Lamarckiana  in  proportions 
which  vary  from  about  1  %  to  less  than  0.1  %.  We  have 
further  seen  that  the  same  mutations  recur  regularly  in 
the  same  mutation  period. 

It  follows  from  this  that  a  careful  study  of  such  a 
period  wnll  soon  reveal  the  commoner  mutants  which 
the  species  in  question  is  producing.  Then  we  have  to 
look  for  the  rarer  ones ;  and  for  this  purpose  much  more 
extensive  sowings  must  be  made. 

If  these  rare  mutations  can  be  recognized  as  seedlings 
or  at  any  rate  as  young  rosettes,  all  that  we  have  to  do  is 
to  sow  seed  on  a  large  scale,  transplant  any  seedlings 
which  exhibit  any  abnormality  and  throw  away  those 
which   have  not   mutated.      If   this  method   is   adopted 


354  Origin  of  Each  Species  Considered  Separately. 

many  thousands  of  plants  can  be  accommodated  on  a  few 
square  meters  of  ground  up  till  the  time  when  the  mu- 
tants have  to  be  planted  out. 

But  if  the  characters  do  not  develop  whilst  the  plant 
is  young,  it  is  a  very  different  matter  indeed.  In  this 
case  40  to  50  is  the  maximum  number  of  plants  that 
can  flower  on  a  square  meter,  and  that  is  a  high  estimate. 

When  this  is  the  case  the  plants  must  be  cultivated 
on  an  enormously  extensive  scale  before  we  can  enter- 
tain the  smallest  hope  of  seeing  mutations.  We  become 
dependent  to  a  large  extent  on  chance  as  in  the  case  of 
the  first  appearance  of  O.  gig  as. 

It  is  obviously  for  reasons  of  this  kind  that  practically 
all  my  mutations  are  recognizable  as  seedlings,  whilst 
the  two  new  species  which  are  found  at  Hilversum  are 
indistinguishable  in  their  young  stages  from  young  0. 
Lamarckiana. 

Oenothera  leptocarpa  is  the  only  exception  to  this 
rule,  at  least  it  is  the  only  one  among  those  which  have 
arisen  from  the  pure  stock  of  O.  Lamarckiana.  Amongst 
the  crops  raised  from  crossed  seeds  there  were  occa- 
sional instances ;  but  it  is  often  difficult  in  these  cases  to 
distinguish  mutations  from  the  ordinary  products  of 
crossing. 

0.  leptocarpa  cannot,  even  in  pure  cultures,  be  dis- 
tinguished from  O.  Lamarckiana  either  as  a  seedling  or 
as  a  rosette  or  even  at  the  period  when  it  is  first  devel- 
oping its  stem.  I  have  once  or  twice  transplanted  sup- 
posed mutations  as  young  plants  and  found  them  to  be 
O.  leptocarpa.  But  as  a  rule  I  have  not  recognized  them 
until  just  before  they  flowered. 

For  these  reasons  little  can  be  said  with  certainty 
about  the  frequency  with  which  this  form  appears.    The 


Oenothera  Leptocarpa.  355 

origin  of  two  examples  of  this  species  will  be  found 
recorded  in  the  pedigree  of  a  branch  of  the  Lamar ckiana- 
family  which  appears  on  page  262.  It  occurred  in  a 
culture  of  about  10,000  seedlings  in  1895,  of  which 
about  a  thousand  flowered.  This  indicates  a  frequency 
of  about  0.2  %.  I  have  noted  the  appearance  of  single 
individuals  both  before  and  after  this,  but  have  not  the 
data  from  which  to  calculate  the  frequency  of  their  oc- 
currence. 

0.  leptocarpa  has  arisen  from  O.  riihrinervis,  as  well 
as  from  0.  Lamar ckiana,  but  not  from  any  other  new 
species.  After  I  had  become  familiar  with  this  fact 
I  found  them  fairly  frequently.  A  character  peculiar  to 
0.  leptocarpa  is  that  it  flowers  very  late — a  character 
which  has  greatly  diminished  the  prospect  of  discovering 
the  species.  For  as  soon  as  the  plants  on  a  bed  begin 
to  flower,  seed-parents  are  chosen  for  self-fertilization. 
And  I  generally  remove  a  certain  number  of  the  plants 
surrounding  these  either  to  allow  them  to  grow  more 
freely  or  to  have  plenty  of  room  for  my  operations.  This 
involves  the  destruction  of  the  weaker  plants  with  which 
the  late  flowering  leptocarpa  are  easily  confused. 

The  riihrinervis  cultures  were  usually  made  with  a 
rather  special  end  in  view  and  therefore  consisted  of  no 
more  plants  than  were  wanted  as  seed  parents.  The 
plants  were  grown  for  example  for  the  purpose  of  mak- 
ing certain  crosses  which  I  had  decided  upon  or  for  the 
experiments  with  tricotyly  which  I  have  already  men- 
tioned, and  in  these  latter  of  course  selection  took  place 
directly  the  seed  came  up.  So  that  the  proportion  in 
which  leptocarpa  appears  in  such  cultures  is  no  indica- 
tion at  all  of  what  the  mutation-coefficient  of  that  species 
really  is. 


356   Origin  of  Each  Species  Considered  Separately. 

For  example  in  1895  I  found  5  leptocarpa  amongst 
44  tricotylous  nihrinervis  (p.  273)  and  in  1897  I  found 
one  amongst  20.  In  1900  I  had  planted  out  24  apparent 
Lamarckiana  plants  which  had  sprung  from  a  cross  which 
I  had  made  in  1899  between  O.  nihrinervis  and  O.  nanella. 
When  they  came  to  flower,  however,  it  turned  out  that 
only  half  of  them  were  really  Lamarckiana  and  that  the 
rest  were  leptocarpa.  In  the  same  year  two  leptocarpa 
appeared  among  the  90  offspring  of  a  cross  between  0. 
nihrinervis  and  0.  Lamarckiana. 

The  most  characteristic  features  of  O.  leptocarpa 
are  its  late  flowering  and  its  long  slender  fruits.  The 
late  flowering  is  not  the  result  of  arrested  growth  for 
the  plants  are  just  as  strong  and  as  tall  as  others  when 
these  are  about  to  flower;  but  it  is  due  to  the  fact  that 
after  they  have  reached  this  stage  they  continue  to  grow 
vegetatively  for  some  weeks  to  come.  The  first  flower- 
bearing  node  is  therefore  considerably  higher  in  lepto- 
carpa than  in  other  forms  and  the  spike  of  flowers 
standing  well  above  those  of  the  other  plants  on  the 
bed  enables  us  to  detect  the  species  immediately.  The  stem 
is,  moreover,  rather  flaccid  so  that  the  flowering  spike 
hangs  over  to  one  side.  The  flowers  and  buds  do  not 
differ  in  any  essential  feature  from  those  of  0.  La- 
marckiana; the  buds  are,  just  before  they  open,  a  slightly 
brighter  green  with  less  yellow  in  them.  The  fruits  and 
bracts  on  the  other  hand  are  quite  different.  The  bracts 
are  broader  at  their  base,  more  triangular  and  more 
flattened,  whilst  those  of  0.  Lamarckiana  are  often  more 
or  less  bent  and  wavy  along  the  midrib.  They  are  pressed 
much  more  closely  against  the  stem  which  they  almost 
completely  enclose  in  a  mantle,  as  it  were:  instead  of 
hanging  down   they  stand  up   fairly   straight.      Finally 


Oenothera  Leptocarpa.  357 

they  are  covered  with  numerous  small  pits  which  tend  to 
alter  the  color  of  the  leaf. 

The  fruits  are  long  and  thin,  and  therefore  quite  dif- 
ferent from  those  of  O.  rubrinervis.  They  seldom  ripen 
because  the  plant  flowers  so  late.  In  November  1896 
I  measured  the  length  and  breadth  of  the  first  five  ripe, 
or  at  any  rate  full  grown,  fruits  on  a  number  of  plants 
of  0.  leptocarpa  which  occupied  two  beds.  I  divided  the 
breadth  by  the  length  and  employed  the  quotient  as  a 
measure  of  the  thickness.  The  values  which  I  got  were 
quite  definite ;  the  mean  thickness  lay  between  1 5  and  1 7 
whereas  that  of  Lamarckiana  ranges  between  22  and  24. 
Thus  we  see  that  the  carpels  of  O.  leptocarpa  are  about 
%  as  thick  as  those  of  the  parent  species. 

The  following  are  the  values  which  I  obtained : 


BREADTH 

—                TJITATT^TrT? 

1896 

OF  INDTVIDTIAT  S 

LENGTH 

— '                        J. 'I   KJ 

A 

B 

12 

0 

1 

13 

1 

3 

14 

5 

3 

15 

6 

8 

16 

11 

2 

17 

15 

3 

18 

13 

5 

19 

3 

1 

20 

5 

1 

21 

2 

0 

22 

2 

1 

23 

1 

0 

24 

0 

0 

Totals 

64 

28 

mean 

17 

15 

The  culture  A  was  from  the  seeds  of  the  two  lepto- 
carpa mentioned  on  p.  262;  B  from  an  artificially  self- 


358   Origin  of  Each  Species  Considered  Separately. 

pollinated  individual  in  a  parallel  culture  in  the  same 
year. 

It  only  remains  to  be  stated  that  in  these  two  cultures 
the  0.  leptocarpa  came  true  to  seed.  In  fact  this  can  be 
clearly  seen  from  the  above  two  columns  of  figures;  the 
individuals  measured  obviously  form  a  definite  group, 
although  their  curve  of  individual  variability  naturally 
overlaps  that  of  O.  Lamarckiana  whose  mode  is  at  22-24. 
The  curves  are  transgressive,  as  is  so  often  the  case  in 
closely  allied  species.^  The  thickest  fruits  of  O.  lepto- 
carpa are  thicker  than  the  thinnest  of  0.  Larnarckiana, 
so  that  if  we  only  had  this  character  to  go  by  we  should 
sometimes  be  unable  to  distinguish  the  tw^o  species. 

Culture  A  consisted  of  300  and  B  of  150  plants  and 
all  of  them,  even  those  which  did  not  ripen  their  fruits 
exhibited  the  characters  peculiar  to  O.  leptocarpa  with  the 
single  exception  of  two  O.  nanella.  Some  of  the  plants 
were  perfectly  pure  leptocarpa  whilst  others  approached 
the  characters  of  the  parent  species  to  a  certain  degree. 
For,  all  the  characters  of  the  species  exhibit  individual 
variability  just  as  we  have  seen  the  thickness  of  the 
fruits  to  do. 

In  spite  of  this  transgressive  variability  the  constancy 
of  the  new  species  was  proved  by  the  cultures.  There  was 
no  real  reversion. 


§  17.    OENOTHERA  SEMILATA. 

This  species  has  only  appeared  thrice  in  my  cultures ; 
and  every  time  from  0.  lata.  One  appeared  in  1894, 
the  other  two  in  two  independent  cultures  in  1895.  They 
looked  very  much  like  0.  lata  except  that  the  characters 

^  On  this  point  see  §  25  of  this  Part. 


Oenothera  Semilata.  359 

of  that  species  were  only  slightly  developed.  Hence  the 
name  semilata.  The  1894  plant  was  broken  in  a  storm. 
One  of  the  1895  ones  flowered  well  but  at  first  set  no 
fruit.  It  was  not  until  November  when  it  had  attained 
a  height  of  2  meters  that  some  good  fruits  were  de- 
veloped, but  the  oncoming  winter  prevented  the  ripen- 
ing of  the  seed. 

I  was  more  fortunate  with  the  third  plant.  It  had 
arisen  in  1895  from  the  first  lata-family;  and  had  there- 
fore O.  lata  as  mother  and  grandmother,  and  0.  La- 
marckiana  as  father  and  grandfather.  See  the  pedigree 
on  p.  285.  At  first  they  only  differed  but  little  from  the 
real  lata  of  the  same  culture,  the  buds  were  however 
slightly  thicker,  the  inflorescence  looser  and  longer,  the 
leaves  narrower  and  slightly  more  rounded  at  the  tip. 
But  when  the  flowers  opened  it  was  found  that  the  anthers 
produced  apparently  good  pollen  although  not  so  much 
as  is  produced  by  O.  Lamarckiana.  I  then  enclosed  the 
plant  in  a  parchment  cover  and  selfed  the  flowers.  I 
also  pollinated  two  pure  latas  with  the  pollen  of  this 
plant.  The  pollen  proved  to  be  quite  good,  for  in  both 
cases  the  plants  yielded  a  good  harvest  of  seed. 

I  sowed  the  self-fertilized  seeds  of  the  semilata  plant 
in  1897.  The  resulting  culture  consisted  of  276  plants 
which  flowered  and  82  which  did  not.  There  occurred 
amongst  them  three  dwarfs  (O.  nanella),  three  lata 
plants  which  flowered,  and  a  rosette  which  evidently  be- 
longed to  the  same  species.  The  nanella  were  obviously 
mutants,  the  lata  either  this  or  perhaps  reversions.  The 
remaining  plants  clearly  exhibited  the  characters  of  semi- 
lata and  justify  the  establishment  of  this  form  as  a  con- 
stant species.  But  I  did  not  consider  the  experiment 
important  enough  to  continue. 


360   Origin  of  Each  Species  Considered  Separately. 

The  above  mentioned  cross  0.  lata  X  0.  semilata  did 
not  give  any  particularly  remarkable  result;  amongst  105 
seedlings  there  were  39  lata,  2  nanella,  2  ohlonga^  and  1 
alb  id  a,  whilst  all  the  rest  were  0.  Lamar  ckiana.  These 
forms  and  the  proportions  in  which  they  occur  are  the 
same  as  those  which  0.  lata  produces  when  crossed  with 
other  species.  These  figures  give  little  support  to  the 
supposition,  which  is  improbable  on  other  grounds,  that 
O.  semilata  is  a  hybrid  or  perhaps  an  intermediate  form 
between  0.  lata  and  0.  Lamarckiana. 


§   i8.     OENOTHERA    NANELLA.      (OENOTHERA    LA- 
MARCKIANA  NANELLA.) 

In  view  of  the  great  importance  which  attaches  to 
a  satisfactory  distinction  between  species  and  varieties 
it  seems  worth  while  to  go  a  little  closely  into  the  differ- 
ence between  Oenothera  nanella^  and  the  other  new  spe- 
cies.^ 

The  new  species,  other  than  nanella,  which  have 
arisen  in  my  experimental  garden  find  no  analogues  either 
in  other  species  of  the  same  genus  or  anywhere  else  in 
the  vegetable  kingdom.  Each  constitutes  a  new  and 
distinct  type  and  is,  without  question,  to  be  regarded  as 
an  elementary  species. 

Varieties   are    distinguished    from   these   in   popular 

'^Oenothera  nanella,  or  the  Dwarf  Evening  Primrose,  often  called 
the  dwarf  for  short,  is  a  constant  form.  The  term  dwarf  is  often 
used  to  signify  the  smallest  individuals,  presented  by  fluctuating 
variability,  which  are  of  course  of  an  entirely  different  nature.  For 
information  on  such  dwarfs  see  P.  Gauchery,  Recherches  sur  le 
nanisme  vegetal,  Ann.  sci.  nat.  hot.,  8  Serie,  T.  IX,  1899,  pp.  61-156; 
and  also  D.  Clos,  Du  nanisme  darts  le  regne  vegetal,  Acad.  Sciences 
Toulouse,  T.  XI,  1389. 

^  For  further  details  see  the  second  volume  of  this  work. 


Oenothera  Nanclla. 


361 


estimation  first  as  being  derived  forms  and  secondly  by 
the  supposed  fact  that  they  do  not  come  true  to  seed 
but  from  time  to  time  revert  to  the  type  of  the  species. 
This  latter  view  has  long  been  shown  to  be  baseless ;  for 
many  varieties  are  just 
as  constant  as  the  best 
species.  Varieties  are  re- 
ally distinguished  by  the 
fact  that  the  same  vari- 
ation recurs  in  a  great 
number  of  species  and 
genera.  The  type  is  not 
new  but  appears  under  a 
variety  of  forms. 

Let  us  apply  this  to 
our  dwarf  Oenothera. 
Dwarf  varieties  are  as 
numerous  as,  for  exam- 
ple, glabrous  ones.  The 
following  are  some  well- 
known  examples,  Tage- 
tes  patiila  nana,  Tagetes 
signata  nana,  Scabiosa 
atro purpurea  nana,  Pap- 
aver  somniferiiin  nanum, 
Dianthus  caryophylliis 
nanus,  Dianthus  barba- 
tus  nanus,  Cheiranthus 
cheiri  nanus,  Matfhiola 
incana  nana,  Calliopsis  bicolor  nana,  Cuphea  purpurea 
nana,  Impatlens  Balsamina  nana  and  many  others.^  Most 
of  them  are  very  popular  garden-flowers. 

*  See  List  in  Carriere,  Production  et  Fixation  des  Varietes,  p.  lO. 


Fig.  yy.  Oenothera  nanella.  Entire 
plants  with  flowers  and  almost 
fully  grown  fruits.   Va  nat.  size. 


362   Origin  of  Each  Species  Considered  Separately. 

From  the  systematic  point  of  view  therefore  our 
dwarf  should  be  called  Oenothera  Laniarckiana  nana  or 
as  it  is  particularly  small,  0.  Lam.  nanella.  But  from 
the  experimental  point  of  view  it  behaves  just  like  the 
other  elementary  species ;  for  it  is,  as  already  stated  in 
§  3,  absolutely  true  to  seed.  And  as  the  name  O.  nanella 
cannot  refer  to  anything  else  I  shall  usually  employ  it.-^ 
If  we  look  a  little  more  closely  into  it  we  shall  find 
other  grounds  for  regarding  our  dwarf  as  an  elementary 
species.  In  the  first  place  it  is  by  no  means  a  miniature 
edition,  as  it  were,  of  0.  Lamarckiana. 


Fig.  78.  Oenothera  nanella.  A,  a  seedling  with  two 
leaves ;  c,  the  cotyledons.  B,  an  older  seedling 
showing  the  long-stalked  leaves  or  flag-leaves,  of 
the  atavistic  period,  which  appear  next  after  the 
first  leaves. 


On  the  contrary  it  is,  like  the  other  new  species,  dif- 
ferent from  it  in  almost  all  its  characters.  It  cannot  be 
mistaken  for  a  weak  plant  of  the  parent  species  at  any 
time.  Or  to  express  it  more  emphatically,  if  we  reduce 
pictures  of  Lamarckiana  and  dwarfs  to  exactly  the  same 
size  we  find  that  we  can  distinguish  them  by  perfectly 
definite  characters. 

^  I  recall  in  this  connection  Darwin's  aphorism :  Varieties  are 
only  small  species. 


Oenothera  Nanclla.  363 

The  dwarfs  can  be  recognized  not  only  as  early  as 
the  rosette  stage  but  even  when  the  first  leaf  is  developed 
(Fig.  7^  A).  This  first  leaf  is  broader  and  has  a  broader 
base  and  a  much  shorter  petiole  than  that  of  0.  La- 
inarckiana.  The  same  is  true  of  the  second  leaf.  The 
result  of  this  is  a  compact  appearance  in  the  young  plant 
which  makes  it  possible  to  record  them  in  the  seed  pans, 
if  the  seeds  have  been  sown  so  far  apart  that  the  seed- 
lings only  just  touch  one  another.  Of  course  there  are 
often  one  or  two  doubtful  individuals  left  over,  as  for 
example  when  the  seedlings  are  crowded  together  in 
groups ;  but  the  doubt  can  always  be  removed  by  growing 
the  plants  in  question  a  few  stages  further. 

The  stage  we  have  just  described  is  followed  by  an 
atavistic  period.  The  dwarf  characters  disappear  and 
it  looks  as  if  the  little  plants  aspired  to  become  tall  La- 
marckianas.  There  appear  two,  three,  or  four  narrow 
leaves  set  on  long  petioles  (Fig.  7SB,  v.  v.  v.);  they 
conceal  the  two  first  leaves  which  are  much  smaller,  and 
so  determine  the  general  appearance  of  the  plant  for  a 
short  time.  But  this  stage  is  soon  shown  to  be  a  transi- 
tory one  by  the  appearance,  in  the  center  of  these  leaves, 
of  the  compact  rosette  of  the  regular  dwarf  type.  (Fig. 
78  B,  and  Fig.  79  A). 

This  so-called  atavistic  period  is  very  common  in 
seedlings.^  We  are  all  acquainted  with  the  fact  that 
seedlings  of  species  of  Acacia  with  phyllodes  have  pin- 
nate and  doubly  pinnate  leaves ;  a  fact  which  enables 
us  to  derive  the  species  in  question  from  doubly-pinnate 
ancestors.  The  seedlings  of  Ulex,  Sarothaninus  and 
those  Papilionaceae  which  lack,  or  have  rudimentary,  fo- 

^  See  the  excellent  summary  of  these  phenomena  in  Goebel's 
Organographie,  I,  1898,  pp.  121-151. 


364   Origin  of  Each  Species  Considered  Separately. 

liage  behave  in  the  same  way.-^  Another  striking  example 
is  afforded  by  the  decussate  arrangement  of  the  leaves 
of  young  trees  of  Eucalyptus  Glohidus,  a  species  which  in 
adult  life  has  long-stalked  leaves  arranged  on  a  different 
plan.-  Siiun  lati folium  and  Berula  angustifolia  have  in 
adult  life  simply  pinnate  leaves  but  in  youth  the  broad 
compound  leaves  which  are  characteristic  of  other  Um- 
belli ferae,  and  therefore  evidently  are  like  those  of  their 
ancestors.  There  are  numerous  other  examples^  of  spe- 
cies which  exhibit  the  characters  of  the  systematic  group 
to  which  they  belong  as  special  characters  of  their  early 
stages.     These  are  the  truest  cases  of  atavism. 

The  d\NdiVi-0 enothera  is  another  example  of  a  species 
which  behaves  in  this  way.  With  this  difference,  that  in 
this  case  the  ancestry  is  known  by  direct  observation 
whilst  in  the  other  cases  it  has  only  been  deduced  from  a 
comparative  study.  But  the  important  point  is  that  in 
this  respect  0.  nanella  behaves  as  an  ordinary  species,  or 
rather,  what  is  much  more  important,  that  the  best  sys- 
tematic species  behave  in  the  same  way  in  respect  of  this 
form  of  atavism,  as  elementary  forms  which  have  just 
arisen  from  the  parent  t3^pe. 

It  is  usually  during  this  "atavistic"  stage  that  the 
fate  of  the  plant — whether  annual  or  biennial — is  de- 
cided. If  the  former,  the  stem  begins  to  be  formed  al- 
most immediatel}^ ;  the  elongate  leaves  are  a  kind  of  prep- 
aration for  this,  for  the  leaves  which  clothe  the  lower 
part  of  the  stem  are  of  this  form  as  is  shown  in  the  left 

^J.  Reinke,  Untersuchungcn  iibcr  die  Assimilationsorgane  der 
Leguininosen,  Jahrb.  fiir  wissensch.  Botanik.  Bd  XXX,  Heft  I  uiid 
4,  1 896- 1 897. 

^  F.  Delpino,  Teoria  generale  dclla  HUotassi,  Geneva,  1883,  p.  242. 

'  For  the  Conifers  see  L.  Beissner,  Handhuch  der  Nadelhoh- 
kunde,  1891. 


Oenothera  Nanella.  365 

figure  in  Fig.  45  on  page  236.  If  the  rosette  is  to  become 
biennial  and  if  tlie  conditions  of  growth  are  favorable 
which  practically  means,  if  the  rosette  has  plenty  of  room 
to  grow  in,  it  begins  to  develop  broader  and  shorter 
stalked  leaves  and  is  recognizable  at  once,  and  from  any 
distance,  as  a  dwarf  rosette.  The  leaves  are  often  not 
much  longer  than  7-8  cm.  at  this  age  whereas  the  radical 
leaves  of  Lamarckiana  often  attain  a  length  of  30  cm. 
or  more. 

This  atavistic  stage  is,  however,  more  often  succeeded 
by  a  rosette  stage  which  lasts  well  on  into  June  but,  if 
the  plant  is  going  to  be  an  annual,  comes  to  an  end 
then.  During  this  period  the  leaves  are  again  very  broad 
and  attached  to  the  short  stem  of  the  plant  by  a  broad 
base.  Their  form  is  often  triangular,  the  leaves  being 
almost  as  broad  as  they  are  long.  If  the  plants  have 
plenty  of  room,  the  outer  leaves  are  pressed  close  against 
the  ground.  The  outer  leaves  at  this  stage  have  quite 
short  stalks  (Fig.  79  A),  the  inner  ones  however  are 
almost  sessile,  almost  ensheathing  the  others  with  their 
broad  bases.  A  full-grown  leaf  of  a  rosette  of  this  age, 
with  its  petiole  is  shown  in  Fig.  52  on  page  293  at  n. 

But  if  the  plants  are  growing  so  thickly  that  they  are 
cramped  for  room,  their  whole  appearance  becomes  quite 
different  but  none  the  less  recognizable  (Fig.  79  B).  The 
leaves  which  make  their  appearance  after  the  "atavistic" 
stage  (v.  V.)  stand  more  or  less  erect,  are  somewhat  nar- 
rower and  have  longer  petioles  but  are  still  set  on  the  stem 
by  a  broad  base.  The  result  is  that  the  stalks  seem  to  be 
twisted  in  a  curious  way  which  is  not  brought  out  clearly 
in  the  figure,  but  which  is  so  characteristic  a  feature  of 
the  young  plant  that  it  is  by  this  character  that  the  young 
dwarfs  are  usually  first  identified ;  and  they  differ  from 


366   Origin  of  Each  Species  Considered  Separately. 

individuals  of  0.  Laniarckiana  of  the  same  age  in  other 
respects  as  well.     (See  Fig.  64  on  page  325.) 

I  have  recorded  the  young  plants  in  any  one  of  the 
four  stages  (Figs.  78  and  79)  according  to  circum- 
stances. The  further  apart  the  seeds  are  sown  the  sooner 
can  the  recording  be  done.  But  even  when  they  are  sown 
thin  a  few  seeds  occasionally  fall  close  together ;  so  that 
we  find  groups  of  seedlings  which  cannot  be  identified 
until  long  after  the  others  have  been  recorded  and  re- 
moved. It  is  often  from  4  to  6  weeks  before  the  last 
individuals   have    fully   developed    their   characteristics. 


Fig.  79.  Oenothera  nanella.  Young  rosettes  in  May  and 
June.  A,  from  seeds  sown  thin;  B,  from  seeds  sown 
thick ;  V.  v.  the  long-stalked  leaves  of  the  atavistic  period. 

Indeed  I  have  often  had  to  transplant  the  seedlings  be- 
fore I  could  be  certain  about  them :  when  I  did  this  I  gave 
them  ample  room  and  grew  them  for  about  a  month  more 
in  the  boxes.  If  I  recognized  a  plant  as  a  dwarf-mutant 
in  a  culture  of  another  species  I  kept  it  until  it  had  at- 
tained the  stage  shown  in  Fig.  79  A  ;  and  usually  trans- 
planted it  to  watch  its  further  development.  If  on  the 
other  hand  it  was  merely  a  question  of  finding  out 
whether  any  Lamarckianas  occurred  in  sowings  of  0. 
nanella  (as  they  often  did  after  fertilization  in  the  open) 


Oenothera  Nanella.  367 

the  recording  was  usually  done  at  an  earlier  age.  For 
it  is  obvious  that  the  earlier  this  can  be  done  the  greater 
is  the  number  of  individuals  that  can  be  dealt  with. 

When  the  seeds  are  sown  in  beds  and  not  in  boxes, 
as  they  usually  were  at  first,  we  must  of  course  await 
either  the  full  development  of  the  rosette  or  if  they  be- 
come annuals,  the  production  of  a  stem. 

The  characters  described  have  enabled  me  to  obtain 
the  figures  already  given,  as  to  the  repeated  appearance 
of  O.  nanella  from  O.  Lamar ckiana  and  from  other  new 
species.  I  propose  to  give  these  figures  again  together 
with  results  obtained  in  certain  other  cultures  in  order  to 
convey  some  idea  of  the  frequency  of  nan^/Za-mutations. 

The  fact  that  they  appear  every  year,  and  in  numbers 
which  become  greater  in  proportion  as  the  sowings  are 
more  extensive  is  proved  by  the  tables  given  in  §§  2-7; 
so  that  I  shall  have  no  occasion  to  refer  to  it  again. 

INDIVIDUALS  OF  O.   NANELLA  V/HICH   HAVE  ARISEN  BY 

MUTATION. 

I.    FROM    OENOTHERA    LAMARCKIANA. 

THE  ORIGIN  OF  THE 

YEAR 
LAMARCKIANAS: 

Lainarckiana-idcrmiy     .  1889-1899 
A  branch  of  the  same  .       1895 
Laemfolia-tamily     .     .       1889 
Various  crosses  (p.  300)      1898 
O.  scintillans  ....  1897-1898 
A  biennial  culture    ,     .       1897 
Culture  of  plants  with 
variegated  leaves  .     .       1899 

Totals    70,154  340  0.5 

The  proportion  of  dwarfs  produced  by  Lamarckiana 
is — if  we  neglect  the  laevifolia-ia.mi\y  where  it  is  possible 
that  other  factors  may  have  come  into  play — a  fairly 


TOTAL  OF 
SEEDLINGS 

NANELLA 

NAN.    % 

50,000 

158 

0.3 

10.000 

111 

1.1 

400 

12 

3.0 

4,599 

26 

0.6 

1,654 

15 

0.9 

1,529 

9 

0.6 

1,972 

9 

0.5 

368   Origin  of  Each  Species  Considered  Separately. 

constant  one;  moreover  It  seems  to  make  no  difference 
whether  the  Lamarckianas  are  of  pure  strain  or  the  off- 
spring of  crosses. 

This  conclusion  is  supported  by  the  proportions  in 
which  O.  nanella  occurs  in  crops  raised  directly  from 
crosses,  that  is,  in  the  first  generation  after  the  cross. 
The  foregoing  table  referred  to  the  second  generation 
from  artificial  crosses,  or  from  free  crossing  as  in  the 
case  of  O.  laczi folia. 

INDIVIDUALS  OF  O.   NANELLA  WHICH  HAVE  ARISEN  BY 

MUTATION. 


II.    FROM  CROSSES. 

CROSS 

YEAR 

TOTAL  OF 
SEEDLINGS 

NANELLA 

NANELLA    % 

O.  Lam. 

X  0.  biennis 

1900 

80 

1 

1.0 

O,  lata 

X  O.  biefinis 

1899 

299 

2 

0.7 

O.  Lam. 

X  O.  brevistylis 

1898 

293 

5 

1.7 

O.  Lam. 

X  O.gigas 

1899 

100 

2 

2.0 

O.  Lam. 

X  0.  scintillans 

1899 

112 

1 

1.0 

O.  lata 

X  0.  Lam. 

1900 

2000 

3 

0.2 

O.  lata 

X  0.  Lam. 

1895-1900 

2387 

26 

1.1 

O.  lata 

X  0.  brevistylis 

1896-1899 

425 

6 

1.4 

Totals    5696  46  0.8 

If  we  compare  these  figures  with  those  already  given 
for  other  species  we  find  a  striking  agreement  between 
them  and  those  for  0.  ohlonga  (about  1  %)  and  we  may 
therefore  regard  0.  nanella  as  one  of  the  commoner 
forms.  It  may  also  be  regarded  as  parallel  in  this  respect 
with  0.  lata  which  will  be  described  afterward  (§  22)  and 
possibly  with  O.  albida  which  however  appears  in  varying 
proportions.  0.  riihrinervis,  O.  gigas,  and  O.  scintillans 
on  the  other  hand  form  a  quite  distinct  group  of  rarer 
mutations,  whilst  O.  semilata  and  the  other  less  important 
types  form  a  third  group  of  still  rarer  deviations. 


Oenothera  Nanella.  369 

O.  nanella  has  arisen  from  other  new  species  in  about 
the  same  proportions;  from  leptocarpa  in  1896  in  a  pro- 
portion of  0.4  %,  from  O.  scintillans  in  various  experi- 
ments from  1896-1899  also  in  a  proportion  of  OA  fo 
(There  were  29  nanellas  amongst  7872  seecUings). 

The  progeny  of  nanella  mutants  come  true  to  seed. 
I  have  observed  over  400  examples  of  this  species  which 
have  arisen  directly  from  other  forms.  Together  they 
obviously  constitute  a  species  which  can  at  once  be  rec- 
ognized by  many  characters,  although  every  one  of  them 
was  different  from  its  parents  and  ancestors. 

I  have  already  in  §  3,  p.  238,  given  the  most  im- 
portant facts  relating  to  the  constancy  of  this  form.  It 
only  remains  to  amplify  the  brief  account  of  the  experi- 
ments given  above. 

I  have  made  four  series  of  experiments  on  the  con- 
stancy of  0.  nanella.  I  began  the  first  of  them  in  1889 
with  the  twelve  mutants  from  the  laevifolia-isimily  men- 
tioned above  (273).  As  I  was  not  familiar  with  parch- 
ment bags  at  that  time  I  was  not  able  to  guard  my  plants 
against  the  visits  of  insects  although  I  always  grew  them 
on  a  bed  which  was  isolated  as  much  as  possible.  But 
even  so,  the  dwarf  type  proved  heritable  in  a  very  high 
degree.  I  harvested  the  first  seeds  in  1890  as  the  plants 
did  not  flower  till  the  second  year.  I  raised  20  plants, 
of  which  18  were  dwarfs;  they  flowered  the  same  sum- 
mer and  set  plenty  of  seed.  This  seed  (about  6  ccm.) 
I  sowed  on  a  bed  of  about  4  square  meters.  The  culture 
consisted  almost  entirely  of  dwarfs.  After  this  the  plants 
flowered  regularly  in  the  first  summer  so  that  I  obtained 
the  fourth  generation  in  1893  and  the  fifth  in  1894.  The 
third  consisted  of  400  plants  which  were  practically  all 
dwarfs;  I  fertilized  some  of  these  with  their  own  pollen 


370   Origin  of  Each  Species  Considered  Separately. 

by  enclosing  them  in  bags.  As  a  result  of  this,  absolute 
purity  of  the  cultures  was  attained  in  1894.  A  culture 
of  440  which  flowered  during  August  and  September 
consisted  entirely  of  dwarfs. 

I  have  not  continued  this  experiment  further  because 
it  seemed  to  me  more  important  to  work  with  the  mu- 
tants themselves  and  to  test  the  constancy  of  the  first 
generation. 

In  1895  I  used  for  this  purpose  some  nanellas  which 
had  just  arisen  from  the  Lamarckiana-isimily,  and  from 
a  branch  of  it.  I  fertilized  12  of  the  former  and  8  of 
the  latter  with  their  own  pollen  excluding  the  visits  of 
insects  from  them.  I  collected  the  seeds  of  each  plant 
separately,  sowed  them  in  the  following  spring,  and, 
after  a  month,  transplanted  all  the  seedlings  without  ex- 
ception, into  wooden  boxes,  in  manured  soil,  where  they 
would  have  plenty  of  room  to  develop  into  rosettes  like 
that  shown  in  Fig.  79  A  (p.  366).  Some  of  them  which 
were  too  close  together  grew  like  the  type  shown  in  Fig. 
79  B ;  I  removed  the  plants  which  surrounded  these  in 
order  that  they  might  have  room  to  expand  their  leaves 
in.  The  recording,  as  a  result  of  this,  took  place  at  dif- 
ferent times  but  all  during  the  month  of  June. 

The  twenty  seed  parents  of  1895  were  raised  from 
the  seeds  of  nine  separate  plants  of  Lamar ckiana  of  wdiich 
five  belonged  to  the  third  (p.  224)  and  four  to  the  second 
generation  (p.  262).  The  twenty  mutants  themselves 
therefore  belonged  to  the  fourth  and  third  generations. 
In  the  following  tables  I  denote  the  grandparent  by 
Lam.,  the  parent  or  mutant  by  Nan.,  and  the  seedlings 
raised  from  the  seeds  of  these  latter  by  S.  The  letters 
A-E  refer  to  the  five  Lainarckiana-^A^ints  of  the  third 
generation,  L-O  to  those  of  the  second  generation ;  their 


Oenothera  Nanella. 


371 


children  are  the  nanella  mutants  (nan.)  whose  seeds  I 
sowed.  The  number  of  offspring  from  each  separate 
parent  are  recorded  in  the  tables. 


OENOTHERA   NANELLA. 


OFFSPRING  OF 

MUTANTS  FROM  THE 

THIRD 

THIRD 

SECOND 

LAMARCKIANA-GENERATION 

LAM. 

NAN. 

s. 

LAM. 

NAN. 

s. 

LAM. 

NAN. 

s. 

A 

No.  1 

277 

c 

No.  1 

30 

L 

No.  1 

55 

A 

"    2 

124 

( ( 

"    2 

21 

( t 

"    2 

99 

B 

89 

D 

"    1 

80 

i  { 

"    3 

302 

( ( 

"    2 

66 

E 

"    1 

38 

1 1 

"    4 

22 

'  i 

"    3 

292 

t  ( 

"    2 

71 

M 

"    1 

30 

( ( 

"    4 

68 

N 

"    1 

339 

<  ( 

"    5 

34 

O 

"    1 
"    2 

105 
321 

Total  950 


Total  240 


Total  1273 


Altogether  there  were  2463  seedlings  which  w^ere  all 
without  exception  O.  nanella. 

These  results  seem  to  me  to  justify  the  belief  that  the 
remaining  nanella-muta.nts  of  1895  would  also,  if  I  had 
collected  their  seed  and  sown  it,  have  proved  constant. 

One  thing  which  I  learnt  from  these  extensive  sow- 
ings was  that  the  dwarfs  were  recognizable,  and  could 
therefore  be  recorded,  at  a  much  earlier  stage  than  I  had 
imagined  before — viz.,  in  the  pans,  before  the  first  trans- 
planting. Now,  it  is  just  the  transplanting  in  such  ex- 
periments which  is  the  greatest  labor  and  it  is  impossible 
to  hand  it  over  to  an  assistant  on  account  of  the  danger 
of  possible  mistakes,  so  that  this  discovery  opened  up  the 
possibility  of  testing  the  constancy  on  a  much  larger 
scale. 

I  used  for  this  purpose  the  nanellas,  referred  to  on 
page  262,  which  came  up  in  1896  from  seeds  which  had 


372   Origin  of  Each  Species  Considered  Separately. 

remained  a  year  in  the  soil.  Such  plants  also  occurred 
in  the  main  culture  referred  to  on  page  224,  although 
they  are  not  referred  to  there.  I  selfed  38  plants,  in 
bags,  with  their  own  pollen.  They  were  all  mutants  from 
Lamarckiana,  some  with  three,  some  with  two  genera- 
tions of  tall  ancestors.  I  saved  and  sowed  their  seed 
separately ;  and  recorded  the  seedlings  at  the  stage  shown 
at  Fig.  78  B.  Doubtful  ones  were  allowed  to  grow  a 
little  further.  The  average  number  of  seedlings  from 
each  of  the  20  seed-parents  was  500,  the  maximum  was 
860,  and  only  in  three  cases  was  it  less  than  100. 

The  total  number  of  seedlings  was  18649;  they  were 
without  exception  dwarfs.  Three  of  them  were  also  ob- 
long a  and  one  also  elliptica. 

Thus  the  seed-parents  of  the  second  experiment  proved 
themselves  to  be,  like  the  20  of  the  first,  perfectly  con- 
stant. 

It  seemed  to  me  important  to  test  the  constancy  of 
nanellas  from  other  sources.  I  chose  for  this  purpose 
two  plants  from  a  scintillans-isimily.  This  family  arose 
from  the  lateral  branch  of  the  Lamarckiana  group  (p.  262) 
and  indeed  from  the  only  individual  referred  to  there. 
This  was  biennial  and  flowered  in  1896.  I  sowed  some 
of  the  self-fertilized  seed  of  this  in  1898  and  selfed  the 
scinfillans  plants  again  with  their  own  pollen.  From  the 
seed  thus  produced  I  obtained  nine  examples  of  nanella, 
which  I  transplanted  and  selfed.  Only  two  of  them 
however  set  seed.  They  had  two  generations  of  scin- 
tillans  behind  them,  and  behind  these  two  generations 
of  Lamarckiana. 

The  plants  had  become  very  weak;  and  the  harvest 
was  a  meagre  one.  Only  64  seeds  germinated ;  but  they 
were  all  nanella.    This  shows  that  the  dwarfs  even  when 


Oenothera  Nanclla.  373 

they  arise  from  another  new  species,  exhibit  in  the  first 
generation  not  only  the  same  characters  but  are  as  true 
to  seed,  as  those  which  arise  directly  from  Lamarckiana. 

For  testing  the  constancy  of  this  form  under  self- 
fertilization  in  subsequent  generations  I  used  the  second 
of  the  above  mentioned  experiments  as  a  starting-point 
(p.  371 ).  Some  of  the  2463  plants  mentioned  there  were 
chosen  as  seed  parents  and  self-fertilized.  The  seeds 
gathered  from  4  of  them  were  sown  in  1897 ;  they  gave 
respectively  94,  135,  154  and  164  seedlings — 547  in  all — 
which  proved  without  exception  to  be  dwarfs  when  they 
were  recorded  as  large  rosettes  m  July.  I  allowed  about 
100  of  these  to  flower  and  fertilized  some  of  them  with 
their  own  pollen.  In  1898  I  raised  from  the  seed  thus 
produced  the  fourth  nanella  generation  which  again  was 
perfectly  constant,  and  allowed  about  100  specimens  to 
flower.  The  fifth  and  sixth  generations  (1899  and  1900) 
also  came  perfectly  true  to  seed.  Of  the  total  number 
of  seedlings — about  400  in  1900 — I  allowed  about  70  to 
flower  and  used  about  30  of  these  as  seed  parents. 

Thus  from  the  third  generation  to  the  sixth,  embra- 
cing in  all  over  a  thousand  plants,  there  occurred  no  single 
instance  of  atavism.  The  new  species  must  therefore  be 
regarded  as  perfectly  constant. 

The  constancy  of  nanella  is  however  incomplete  in 
the  sense  that  it  has  inherited  the  capacity  of  mutating, 
from  the  parent  species.  For  it  gives  rise  to  individuals 
which  though  obviously  nanellas  also  betray  the  charac- 
ters of  some  of  the  other  new  species. 

And,  conversely,  it  occasionally  happens  that  dwarfs 
arise  from  other  new  species  and  then  bear  the  characters 
of  both  types  together.  In  this  way  we  get  species  of  the 
second  order,  which  correspond  to  the  cultivated  varie- 


374   Origin  of  Each  Species  Considered  Separately. 

ties  of  the  second  and  third  order  as  described  above.  ^ 

Combinations  of  this  kind  occur  both  in  pure  cultures 
and  in  the  offspring  of  crosses.  The  following  are  the 
cases  which  I  have  observed  so  far. 

Commonest  of  all  were  dwarfs  which  also  bore  the 
characters  of  lata,  developed  to  their  full  extent.  I  no- 
ticed the  first  in  1892  amongst  my  nanellas,  which  were 
at  that  time,  as  I  have  already  stated,  constant  in  every 
other  respect.  There  were  three  plants  which,  like  the 
rest,  were  annual.  They  flowered  amongst  the  others  and 
were  fertilized  with  their  pollen.  They  produced  fruits 
which  however  contained  little  seed.  They  attained  a 
height  of  25  cm.  and  could  be  recognized  even  before 
they  flowered  as  naneUa-lata.  Their  broad  rounded 
leaves,  the  compact  inflorescence  with  broad  bracts,  their 
thick  swollen  buds  and  the  crumpled  petals  of  their  flow- 
ers exactly  resembled  those  of  true  lata.  But  their  seeds, 
resulting  from  fertilization  by  nanella,  gave  rise  to  ordi- 
nary nanella  only 

In  the  sum.mer  of  1896  I  had  another  example  of 
nanella-lata  from  seeds  of  self-fertilized  nanella.  It 
agreed  exactly  with  those  observed  in  1892. 

In  1898  and  1899  the  same  combination  appeared 
amongst  the  offspring  of  two  crosses  (1)0.  Lamarckiana 
XO.  nanella,  (II)  O.  lata  X  O.  nanella.  In  the  first  of 
these  (1898)  there  were  two  examples  amongst  about 
100  dwarfs,  in  the  other  (1899)  only  one  amongst  133 
nanellas  and  79  latas.  The  second  culture  was  under- 
taken solely  with  the  object  of  bringing  about  the  com- 
bination of  the  two  forms  by  crossing.  This  object 
was  attained,  the  characteristic  features  of  the  two  pa- 

^  Compare  for  example  Scahiosa  afropurpurea  nana  purpurea  and 
other  cases  on  p.  197. 


Oenothera  Nanella.  375 

rents  being  fully  developed;  but  only  in  a  single  indi- 
vidual. 

Beside  nanella-lata  I  have  observed  the  following 
combinations : 

COMPOUND    TYPES    OF    OENOTHERA    NANELLA. 
FROM   SEEDS    OF  COMBINATION 

O.  Lamarckiana  X  O.  nanella         O.  7ianella-oblonga  1898 

O.  lata  X  O.  nanella  O.  nanella-albida  1899 

"       "            "        "  O.  nanella-ellipHca  1899 

"       "            "        "  O.  7ia7iella-sciniillans  1899 

O.  nanella  O.  nanella-oblonga  1897 

O.  scintillans  O.  scintillans-nanella  1899 

O.  gigas  O.  gigas-nanella  1897 

O.  Lamarckiana  O.  nanella-ellipiica  1889 

This  list  is  sufficient  to  show  that  the  dwarf-character 
can  be  associated  with  the  characters  of  the  various  other 
new  species.  The  characters  of  these  others  may  also  be 
associated  with  one  another  although  this  is  very  rarely 
the  case.  This  difference  between  0.  nanella  and  other 
species  is  doubtless  intimately  connected  with  the  varietal, 
as  opposed  to  specific,  character  of  0.  nanella  ^vhich 
marks  it  off  from  all  the  other  new  species. 

If  we  regard  nanella  as  a  variety  we  should  expect  it 
to  arise  from  any  of  the  new  species  just  as  much  as  from 
O.  Lamarckiana  itself.  And  it  should  be  noted  in  this 
connection  that,  of  the  6  combinations  mentioned,  only 
one  arose  from  the  seeds  of  nanella. 

I  shall  now  give  a  description  of  the  flow^ers  of  the 
dw^arf  (Fig.  77,  p.  361). 

These  are  remarkably  large  compared  with  the  size 
of  the  plants,  especially  in  the  case  of  vigorous  biennial 
individuals.  On  the  latter  they  attained  to  very  nearly 
the  size  of  the  flowers  of  O.  Lamarckiana.  On  plants 
which  flower  in  the   first  year  they  are  usually  much 


376  Origin  of  Each  Species  Considered  Separately, 


smaller  in  correspondence  with  the  greater  weakness  of 
the  whole  plant.  The  petals  commonly  measure  only  2%  X 
4  cm.,  as  opposed  to  the  3X5  cm.  of  Lamarckiana. 

On  annual  plants  some  of  the  flowers  are  often  in- 
completely developed.  As  a  rule  only  one  or  two  flow- 
ers on  a  plant  are  affected  in  this  way.  Sometimes  there 
is  very  little  pollen,  sometimes  none  at  all;  very  often 
it  happens  that  the  stigmas  cannot  separate,  and  remain 

close  together.  This  stig- 
matic  group  is  often 
quite  small  and .  some- 
times blackens  and  shriv- 
els up  before  pollination. 
Or  again,  the  style  may 
be  so  short  that  it  does 
not  protrude  from  the 
corolla.^ 

A  striking  abnormal- 
ity is  an  oblique  position 
of  the  buds  on  the  calyx 
tube  (Fig.  80).  The 
calyx  is  bent  sideways 
in  such  a  manner  that 
the  bud  is  at  right  an- 
gles to  the  calyx  tube. 
The  opening  of  the  calyx  is  interfered  with  by  this  and 
indeed  often  takes  place  abnormally  or  incompletely.  The 
petals  do  not  unfold  properly  and  the  sexual  organs  are 
more  or  less  sterile. 

These  abnormalities  are  usually  to  be  found  on  the 
lower  flowers  when  the  plant  has  not  attained  a  height 

_^  These  and  other  malformations  of  the  dwarfs  are  often  due  to 
a  disease,  and  as  such,  to  a  large  degree  dependent  on  outer  circum- 
stances. (Note  of  1908.) 


Fig.  80.  Oenothera  nanella.  Buds  at 
the  top  of  the  stem.  At  the  side 
are  shown  the  commonest  malfor- 
mations of  such  buds. 


Oenothera  Scintiltans.  377 

of  more  than  10-15  centimeters.  But  even  the  common 
Lamarckiana  often  produces  some  abnormal  flowers 
amongst  the  lower  ones.  If  the  nanella  survives  this  pe- 
riod and  if  it  becomes  markedly  stronger  it  forms,  first, 
a  shorter  or  longer  intermediate  piece  and  then  a  fine 
head  of  large  flowers.  This  is  borne  by  the  barren  look- 
ing, bracteated,  flowerless  part  of  the  stem,  well  above 
the  lower  half  of  the  inflorescence.  But  it  is  by  no  means 
all  plants  that  are  strong  enough  to  reach  this  state. 

The  best  way  of  raising  fine  plants  of  nanella  is  to 
make  them  biennial  by  sowing  the  seed  late. 


C.    THE  INCONSTANT  SPECIES. 

§  19.    OENOTHERA  SCINTILLANS. 
(Plate  V.) 

As  far  as  we  know,  species  in  nature  are  constant. 
This  is  true  also  of  elementary  species,  and  of  most  so- 
called  varieties.  It  is  true  that  the  older  systematists, 
such  as  Koch,  Spach  and  many  others,  believed  to  be 
able  to  distinguish  varieties  from  species  by  their  in- 
constancy. But  they  seldom  took  the  trouble  to  exclude 
the  visits  of  insects  in  the  numerous  experiments  they 
made.  If  we  take  this  precaution  many  varieties  prove 
to  be  as  constant  as  species. 

The  universal  belief  in  the  constancy  of  species  has 
led  us  to  regard  this  quality  as  one  of  the  attributes  of 
a  species.  From  this  standpoint,  it  would  seem  a  con- 
tradiction in  terms  to  speak  of  an  inconstant  species. 

But  such  a  contradiction  need  only  trouble  adherents 
of  the  current  theory  of  selection.  The  mutation  theory 
can  remove  even  this  difficulty.     Lack  of  constancy  is 


378   Origin  of  Each  Species  Considered  Separately. 

obviously  one  of  the  most  unfavorable  characters  that 
a  species  can  possess ;  and  the  theory  of  selection  which 
can  only  explain  the  origin  of  favorable  characters  can- 
not account  for  the  existence  of  unfavorable  ones. 

According  to  the  mutation  theory  a  species,  even  if 
it  is  so  weak  that  it  can  hardly  maintain  itself,  and  can 
only  just  reproduce  itself,  is  capable  of  existing,  for  a 
time,  alongside  the  parent  species.  Oenothera  hrevistylis, 
which  hardly  sets  any  seed  and  yet  has  maintained  itself 
amongst  the  Lamarckianas  at  Hilversum  since  1887, 
proves  the  correctness  of  this  view.  At  some  future 
date  no  doubt,  if  the  struggle  for  existence  becomes 
keener,  it  w^ill  give  way  to  Lamarckiana  or  be  vanquished 
in  the  struggle  with  other  plants  whilst  Lamarckiana  may 
survive.  But  if  the  conditions  of  life  remain  as  they 
have  been  up  to  now,  there  is  at  least  the  possibility  that 
O.  hrevistylis  may  continue  to  exist  alongside  La- 
marckiana.^ 

This  difficulty  can  be  avoided  by  confining  the  term 
species  to  those  forms  which  have  emerged  victorious 
from  the  struggle  for  existence.  But  such  a  limitation 
of  the  meannig  of  the  term  would  of  course  be  perfectly 
arbitrary  and  only  serve  to  further  confuse  a  problem 
already  sufficiently  difficult. 

The  doctrine  of  mutation  on  the  other  hand  makes 
it  easy  to  see  how  species  may  arise  and  yet  be  disquali- 
fied for  survival  for  any  length  of  time.  Mutability 
produces  deviations  in  all  directions  (I,  §  26,  p.  198)  ;  it 
is  absolutely  uninfluenced  by  the  greater  or  lesser  utilit}^ 
of  the  changes  it  produces.  It  simply  produces  varia- 
tions, leaving  it  to  the  struggle  for  existence  to  decide 
whether  they  are  in  the  right  direction  or  not.     But  the 

^  It  still  occurred  in  that  locality  in  1907.     (Note  of  1908.) 


Oenothera  Scintillans.  379 

event  is  dependent  not  only  on  the  quality  of  the  varia- 
tion but  also  on  the  environment  in  which  it  is  placed. 
The  variations  which  pass  through  the  sieve  of  the 
struggle  for  existence  are  not  different  from,  but  merely 
part  of,  those  which  are  put  into  it. 

The  mutation  theory  admits  of  the  production  of 
such  forms  as  will  sooner  or  later  for  some  reason  or 
other,  perish  without  having  contributed  materially  to 
the  flora  or  fauna  of  a  district.  The  causes  of  such  dis- 
appearance are  mainly  three:  (1)  sterility,  or  at  any 
rate  insufficient  fertility;  (2)  constitutional  delicacy;  (3) 
inability  to  breed  true. 

Nor  is  there  any  a  priori  ground  for  supposing  that 
more  ''fit"  species  arise  than  ''unfit." 

There  have  arisen  in  my  cultures  besides  robust  forms 
like  0.  gigas  and  O.  riihrinervis,  and  weak  ones  like  O. 
ohlonga  and  0.  alhida,  a  series  of  forms  which  were 
either  sterile,  or  were  fertile  but  did  not  come  true  to 
seed.  I  should  have  called  them  transitory  species,  were 
it  not  that  all  species  are  transitory.  I  now  refer  to  the 
former  group  as  infertile  and  to  the  latter  as  inconstant 
species. 

Neither  of  these  types  can  last  long  in  nature.  They 
must  obviously  be  excluded  from  amongst  the  species 
with  which  the  ordinary  investigation  of  nature  familiar- 
izes us.  It  is  only  when  one  can  witness  a  period  of 
mutation  that  there  is  any  chance  of  seeing  such  forms. 

I  propose  to  deal  now  with  some  types  of  inconstant 
species  and  shall  begin  with  the  one  I  have  investigated 
most  thoroughly. 

This  is  Oenothera  scintillans  which  is  figured  on  Plate 
V  and  in  Fig.  47  on  page  244.  I  have  already  stated, 
in  §  3  of  this  section,  that  the  seeds  of  this  species  pro- 


380   Origin  of  Each  Species  Considered  Separately. 

duce  three  different  forms,  0.  scintillans,  O.  ohlonga,  and 
O.  Laniarckiana  even  after  it  has  been  carefully  fertilized 
with  its  own  pollen  and  the  visits  of  insects  have  been 
effectually  excluded.  The  proportion  in  which  O.  scin- 
tillans is  reproduced  is  in  some  cases  about  35-40  %  and 
in  others  about  70  %. 

Before  we  can  estimate  the  effects  of  this  incon- 
stancy we  must  know  what  happens  in  subsequent  gen- 
erations. I  shall  afterwards  give  the  details  of  some  ex- 
periments which  show  that  the  0.  ohlonga  and  0.  La- 
marckiana  thus  produced  are  as  constant  as  those  given 
off  directly  from  the  main  stem  of  the  Laniarckiana-isim- 
ily.  The  scintillans  on  the  other  hand  behave  like  their 
parent,  their  offspring  segregating  in  the  same  way. 

What  will  be  the  composition  of  the  successive  gen- 
erations? We  will  suppose  that  the  plants  are  self- 
fertilized,  that  no  selection  takes  place  and  we  will  put 
the  proportion  of  scintillans  in  each  generation  at  about 
one-third.  And  we  will  limit  the  extent  of  the  genera- 
tions to  a  thousand  plants  each.  The  contents  of  suc- 
cessive generations  will,  then,  obviously  be  :^     . 


\ 

SCINTILLANS 

LAMARCKIANA  +  OBLONGA 

1st  Generation 

333 

667 

2nd 

111 

222  -f-  667  —  889 

3rd 

37 

74  +  889  —  963 

4th 

12 

25  +  963  =  988 

5th 

4 

8  4-  988  —  996 

6th 

1 

3  4-  996  =  999 

7th 

0 

1000 

Therefore  in  a  batch  of  about  1000  plants  all  the 

scintillans  would  have  died  out  after  seven  generations 

without  the  operation  of  any  selective  process.     In  the 

case  before  us  however  the  process  would  be  hastened 

^The  xth  generation  will  contain  (Va)^  scintillans. 


Oenothera  Scintillans.  381 

by  a  very  definite  selection  resulting  from  the  fact  that 
scintillans  is  much  more  delicate  than  Lamarckiana. 

It  is  now  sufficiently  clear  that  a  species  which  pro- 
duces besides  offspring  like  itself  other  constant  types 
must  inevitably  disappear  sooner  or  later. 

If  the  constant  types  appear  in  a  smaller  proportion 
than  we  have  considered  so  far,  in  each  generation,  as  in 
the  case  of  0.  scintillans  producing  70  %  of  its  kind 
(p.  246)  it  will  take  longer  for  the  form  to  disappear; 
but  disappear  it  must.^  It  is  only  by  excelling  its  con- 
stant offspring  in  individual  strength  that  it  can  ever 
stand  a  chance  of  surviving  altogether.  If  it  did  this 
it  would  be  in  the  position  in  which  0.  Lamarckiana 
finds  itself  now  with  regard  to  the  new  species  arising 
from  it. 

These  facts  give  a  simple  explanation  of  the  absence 
(or  perhaps  rather  the  great  rarity?)  of  inconstant  spe- 
cies in  nature.  For  it  is  not  necessary  to  assume  that 
such  do  not  arise  or  even  that  they  do  not  arise  often. 
The  proof  that  they  cannot  maintain  themselves  is  suf- 
ficient. Left  to  themselves  the}^  will  be  reduced  in  a 
very  few  years  to  a  hundredth  or  even  thousandth  part 
of  the  total  of  their  offspring,  and  they  will  very  soon 
be  lost  altogether.  They  can  only  continue  to  exist  by 
being  produced  continuously  or,  at  least,  frequently  by 
the  parent  species. 

The  mutation  theory  renders  the  origin  and  disappear- 
ance of  unfit  types  intelligible ;  moreover  the  actual  origin 
of  such  has  been  observed.  These  cases  constitute  an 
insuperable  obstacle  in  the  way  of  the  theory  of  selec- 
tion. 

*  The  I2th  generation  will  bring  the  form  down  to  about  i  %  ; 
and  generally  speaking  the  xth  to  (Vio)''. 


382   O rig  171  of  Each  Species  Considered  Separately. 

From  these  general  considerations  I  pass  on  to  the 
special  treatment  of  our  first  example  O.  scintillans. 
Fig.  47  and  Plate  V  show  the  flowering  spike  of  annual 
examples  of  the  species ;  the  long,  tapering  budbearing 
internodes  above  the  open  flowers  cannot  fail  to  attract 
attention.  This  feature  stamps  the  habit  of  the  plant 
from  July  to  late  in  the  autumn :  in  most  of  the  other 
species  the  buds  do  not  rise  much  above  the  crown  of 
flowers.     Moreover  the  bracts  in  this  region  are  pretty 


Fig.  8i.  Oenothera  scintillans.  A,  young  plant  with  6 
leaves  above  the  cotyledon.  Bj  young  rosette  at  the  age 
of  two  months. 


large  so  that  the  youngest  part  of  the  stem  is   fairly 
thickly  clothed  with  leaves. 

The  flowers  are  considerably  smaller  than  in  0.  La- 
mar ckiana,  a  circumstance  almost  certainly  due  to  the 
general  delicacy  of  the  species.  Otherwise,  the  struc- 
ture of  the  flowers  resembles  that  of  the  parent  species; 
for  example  the  stigmas  extend  well  beyond  the  anthers 
so  that  the  flowers  are  generally  cross-fertilized. 


Oenothera  Scintillans.  383 

The  development  of  the  anthers  and  the  pollen  is  to  a 
high  degree  dependent  on  external  conditions.  The  pol- 
len is  sometimes  plentiful,  sometimes  scanty,  and  at 
other  times  entirely  absent.  These  variations  occur  on 
one  and  the  same  plant  and  seem  to  depend  chiefly  on 
the  temperature,  inasmuch  as  the  anthers  degenerate 
under  the  influence  of  hot  weather.  It  is  in  consequence 
of  this  circumstance  that  I  have  lost  many  fruits  by  en- 
closing flowers  in  parchment  bags  (to  insure  pure  self- 
fertilization)    in  the   full  sunlight. 


Fig.  82.     Oenothera  scintillans.     A  rosette  ot  radical 
leaves,  at  the  end  of  June. 

The  annual  plants  are  only  very  slightly  branched, 
and  begin  to  flower  when  they  are  only  Yo  meter  high. 
The  lateral  branches  spring  from  just  underneath  the 
flowering  zone,  and  on  them  isolated  flowers  appear 
towards  the  end  of  September  or  even  later.  Biennial 
plants  are  usually  more  branched,  and  if  the  heart  of  the 
rosette  happens  to  have  frozen  in  the  winter  a  circlet  of 


384    Origin  of  Each  Species  Considered  Separately. 

secondary  stems  is  formed.     Biennial  plants  are  in  every 
respect  stronger  and  bear  larger  fruits  with  better  seeds. 

But  the  most  characteristic  feature  of  this  species  is 
its  smooth  shining  dark-green  narrow  leaves. 

The  young  rosettes  are  recognizable  by  this  char- 
acter (Figs.  81  and  82),  and  can  easily  be  distinguished 
by  means  of  it  from  the  species  by  which  they  happen 
to  be  surrounded  (Fig.  52,  p.  293). 

The  leaves  are  not  very  narrow  at  first ;  in  fact  they 
do  not  become  so  until  the  rosettes  are  2  or  3  months 
old.  This  feature  gradually  becomes  more  pronounced 
during  the  summer  whether  the  plant  remains  in  the 
rosette  stage  or  develops  a  stem.  The  midrib  of  the  leaf 
is  broad  and  like  the  leaf  stalk  is  of  so  pale  a  green  that 
it  might  almost  be  called  white,  and  has  not  a  trace  of 
red  color  in  it.  The  leaves  of  the  full  grown  rosette  have 
long  petioles  and  are  about  four  times  as  long  as  they 
are  broad  or  even  narrower.  There  are  no  unevennesses 
on  the  blade  nor  is  there  that  pale  green  bloom  on  them 
which  is  characteristic  of  O.  alhida  and  0.  rtibrinervis ; 
they  are  almost  absolutely  smooth  and  very  different 
from  those  of  Lamar ckiana  in  their  dark  green  color. 
Indeed,  scintillans  bears  very  little  resemblance  to  its 
parent  species  except  in  its  flowers. 

The  leaves  of  the  stem  (Fig.  54,  p.  295)  resemble 
those  of  the  rosette  in  all  essential  points  and  so  do  not 
require  any  special  description. 

In  regard  to  the  mode  of  its  origin  0.  scintillans  re- 
sembles O.  gigas  and  O.  semilata  in  being  one  of  the 
rarest  types.  It  has  only  arisen  14  times  altogether  as 
a  mutation.  Although  most  of  these  instances  have  al- 
ready been  described  it  is  worth  while  summarizing  them 
all  here. 


1  (2) 

14,000 

0 

8,000 

2  (2) 

1,800 

0 

10,000 

1  (2) 

3,000 

0 

164 

1  (1) 

300 

0 

Oenothera  Scintillans.  385 

OENOTHERA   SCINTILLANS. 

INDIVIDUALS    THAT   HAVE   ARISEN    BY    MUTATION. 

SOURCE  YEAR     ^°^^^  °^    O.  SCINTILLANS  P'^ODUCING 

SEEDLINGS  RIPE  FRUIT 

O.  lata 1888 

I  1895 
The  Laniarckiana-ioimWy    -  1896 

(  1897 
Lateral  branch  of  this  family  1895 
O.  Lam. ,  a  subsidiary  culture  1897 

O.  lata 1898 

O.  lata  X  O.  biennis .     .     .  1899 

As  the  last  column  of  the  table  shows  I  only  succeeded 
in  getting  ripe  fruits  from  five  of  these  mutants,  of  which 
four  set  seed  in  the  second  year  (2)  and  only  one  in  the 
first  ( 1 ) .  The  rest  died  as  rosettes  or  at  any  rate  be- 
fore they  fruited.  The  percentage  composition  of  the 
cultures  raised  from  these  seeds  has  already  been  given 
on  pp.  244-246,  but  will  be  described  in  greater  detail 
now. 

I  shall  begin  with  the  oldest.  It  appeared  in  1888 
in  the  /a/a- family  referred  to  on  p.  288;  it  was  biennial 
and  flowered  luxuriantly  in  July  1889  but  was  left  to  be 
fertilized  promiscuously  amongst  a  crowd  of  Lainarc- 
kianas.  It  had  all  the  characters  which  were  afterwards 
observed  both  in  its  offspring  and  in  the  other  mutants. 
I  sowed  its  seed  partly  in  1890  partly  in  1894  and  ob- 
tained, in  both  years,  both  annual  and  biennial  plants. 
The  rosettes  of  1894  flowered  in  1895;  the  plants  were 
self- fertilized  in  parchment  bags.  There  were  14  healthy 
plants,  bearing  hardly  any  branches :  their  fruits  were 
small,  and  did  not  afford  more  than  1  to  3  cubic  centi- 
meters of  seed  per  plant.     The  seeds  were  sown  on  sep- 


386   Origin  of  Each  Species  Considered  Separately. 

arate  beds  and  the  young  plants  recorded  at  the  end  of 
June. 

As  the  seeds  were  sown  thin  and  as  a  great  many 
did  not  come  up,  the  seedHngs  stood  far  apart  and  had 
plenty  of  room  in  which  to  develop  their  characteristic 
features. 

I  counted  :^ 


PER  SEED  PARENT 

TOTAL 

IN   \ 

Seedlings 

16—52 

399 

O.  scintillans 

2—  9 

62 

15 

O.  Laniarckiana 

7—36 

268 

68 

O.  oblofiga 

1—11 

60 

15 

O.  lata 

0—  2 

8 

2 

O  nanella 

0—  1 

1 

This  experiment  showed  that  each  of  the  14  seed  pa- 
rents gave  rise  to  the  three  chief  forms,  when  self- 
fertilized.  They  did  this  moreover,  so  far  as  the  small 
numbers  enable  us  to  judge,  in  not  very  widely  different 
proportions. 

In  this  experiment  the  original  mutant  was  fertilized 
by  insects ;  but  all  the  subsequent  mutants  which  appeared 
were  enclosed  in  parchment  bags,  as  soon  as  they  began 
to  flower,  and  artificially  self-fertilized.  The  first  to  be 
treated  thus  was  the  scintillans,  mentioned  on  p.  262, 
which  appeared  in  1896  in  a  branch  of  the  Lamarckiana- 
family.  Six  stems  were  developed  from  the  axils  of  its 
radical  leaves  and  a  quantity  of  seed  was  set.  I  also 
succeeded  in  taking  cuttings  from  the  remaining  branches 
of  the  rosette :  they  survived  the  winter  and  flowered  in 
the  following  year.  I  sowed  the  1896  seed  partly  in 
1897  and  partly  in  1898,  in  the  former  year  both  in  pans 
and  in  a  bed  in  the  garden.  The  three  crops  raised  in  this 
way  were  composed  as  follows  :^ 

^  See  the  table  on  p.  244.  ^  See  the  second  table  on  p.  245. 


Oenothera  Scintillans.  387 


1897 

1897 

1898 

IN  PANS 

IN  THE  GARDEN 

IN  PANS 

Number  of  seedlings 

572 

275 

165 

Oo  scintillans 

36  % 

34  % 

36  % 

O.  Lamarckiana 

52  % 

52  % 

60  % 

O.  oblonga 

10  % 

13  % 

3  % 

O   lata 

1  % 

1  % 

1  % 

O.  nanella 

1  % 

0 

0 

In  the  summer  of  1897  I  selfed  five  of  the  La- 
marckianas  in  this  culture  with  their  own  pollen.  Each 
bore  from  12-13  cm.  of  seed,  of  which  some  was  sown 
next  year  in  the  garden  and  in  pans.  117  seeds  germinated 
in  the  garden  and  1079  in  the  pans.  There  was  not  a 
single  example  of  scintillans  amongst  these.  The  major- 
ity of  them  were  Lamarckianas,  with  a  considerable  ad- 
mixture of  mutants.  In  the  garden  these  were,  4  O. 
ruhrinervis,  3  O.  lata,  1  0.  nanella,  1  O.  alhida  and  2 
O.  oblonga ;  in  the  pans  the  only  mutants  were  7  ex- 
amples of  O.  nanella. 

The  Laniarckianas,  therefore  which  are  produced  by 
0.  scintillans,  have  the  same  constancy  as  the  original 
Lamarckiana,  that  is  to  say  their  grand-parents,  but  also 
exhibit  the  same  degree  of  mutability. 

The  point  is  that  a  continued  segregation  into  La- 
marckiana, scintillans  and  oblonga  is  not  witnessed  in 
the  seedlings  from  the  Laniarckianas  extracted  from  scin- 
tillans as  it  was  in  the  original  scintillans. 

Of  the  mutants  mentioned  O.  rubrinervis,  0.  lata  and 
O.  nanella  flowered  the  same  summer. 

The  very  important  question  now  presented  itself, 
how  the  scintillans  plants  in  this  generation  behaved  on 
self-fertilization.  To  answer  this  question  I  enclosed 
over  50  plants  of  the  1898  culture  in  bags,  harvested 
their  seed   separately  and  sowed  it.     All   the  seedlings 


388   Origin  of  Each  Species  Considered  Separately. 

were  transplanted,  under  glass  at  first,  in  order  to  give 
them  plenty  of  room  for  the  full  development  of  the 
rosette.  The  rosettes  were  counted  between  the  ages 
of  2  and  3  months,  the  process  lasting  from  the  middle 
of  May  till  the  middle  of  June  (see  Fig.  82).  Alto- 
gether about  5850  rosettes  produced  by  42  plants  were 
recorded.  The  crops  which  contained  less  than  50  seed- 
lings from  a  given  parent  were  recorded  but  not  included 
in  those  from  which  the  following  percentages  were 
counted.  The  average  number  of  seedlings  per  parent 
plant  in  the  cases  dealt  with  is  therefore  about  140. 

The  number  of  scintillans  naturally  varied  from  crop 
to  crop,  as  a  result,  doubtless,  of  the  smallness  of  the 
number  of  seedlings  counted.  I  have  determined  the 
percentage  values  for  each  parent,  and  arranged  them 
in  groups  of  1-10  %,  10-20  %  and  so  on.     I  found: 


NUMBER  OF  SEED  PARENTS 

7  % 

1 

19  % 

1 

21—30  % 

9 

31—40  % 

12 

41—50  % 

15 

51     55  % 

4 

This  gives  an  average  of  40  %,  a  figure  which  agrees 
with  the  coefficient  for  the  grandmother  (36  %)  closely 
enough. 

The  oblongas  in  this  experiment  varied  between  0-12 
per  seed  parent.  There  were  197  of  them  altogether, 
i.  e.,  they  formed  about  3  %  of  the  population.  The  rest 
were,  with  the  exception  of  about  1  %  O.  lata  and  O. 
nanella,  all  O.  Lamarckiana.  We  have  therefore  on  the 
average : 


Oenothera  Scintillans.  389 

SECOND  GENERATION  FIRST  GENERATION 

O.  scintillans  40  %  36  % 

O.  Lamarckiana  56  %  60  % 

O.  ohlonga  3%  3% 

O.  lata  and  nanella  1  %  \  % 

The  agreement  between  the  two  succeeding  genera- 
tions is  as  great  as  can  be  expected  in  an  experiment  of 
this  kind. 

There  were  four  seedparents  with  52,  52,  54  and 
55%  scintillans  in,  respectively  111,  61,  161  and  95 
seedlings.  The  ^aH//7/a/z^-producing  capacity  seems  very 
variable,  but  the  figures  would  perhaps  deviate  less  if 
greater  numbers  had  been  grown.  The  deviation  seems, 
however,  to  lie  within  the  limits  of  individual  varia- 
bility. 

In  1896  six  plants  of  O.  scintillans  arose  in  the  main 
line  of  the  Lamarckiana-family  (p.  224  and  385).  I 
succeeded  in  bringing  two  of  these  through  the  winter 
and  in  getting  them  to  flower  in  1897.  Their  pollination 
was  artificial  and  not  disturbed  by  the  agency  of  insects. 
The  amount  of  seed  set  was  small,  varying  from  %  to 
2  ccm.  per  plant :  is  was  sown,  separately  for  each  seed 
parent,  in  March  1898. 

One  seed  parent  gave  rise  to  365  seedlings  which  in- 
cluded the  same  types  in  the  same  proportion  as  in  the 
previous  experiment.-^  The  other  yielded  a  total  of  only 
about  200,  which  was,  however,  made  up  quite  differ- 
ently.^ 69  %  of  the  population  were  scintillans,  that  is 
to  say  twice  as  much  as  in  the  previous  experiments. 
The  relative  number  of  ohlonga  was  also  doubled  and 
amounted  to  21  %.  The  number  of  Laniarckianas  was 
correspondingly  low,  amounting  to  no  more  than  8  %, 

*  See  the  numbers  on  the  lower  table  on  p.  245. 
'  P.  246. 


390   Origin  of  Each  Species  Considered  Separately. 

whilst  that  of  the  other  mutants  (0.  lata,  0.  nanella,  etc.) 
remained  at  about  2  %. 

There  is  therefore  in  0.  scinfillans  a  highly  fluctuating 
degree  of  the  hereditary  capacity,  if  by  this  term  we  may 
denote  the  different  proportions  in  which  0.  scintillans 
is  able  to  produce  offspring  like  itself. 

The  hereditary  capacity  can  either  be  very  small,  or 
about  35-40  %,  or  as  much  as  69  %  ;  the  latter  figure 
being  about  twice  as  large  as  the  formen  In  the  case 
of  the  former  this  capacity  was  essentially  the  same  in 
the  second  generation  as  it  was  in  the  first,  and  in  the 
case  of  the  latter  the  difference  was  also  very  little. 

This  is  proved  b}^  the  result  of  the  continuation  of  the 
experiment  we  are  dealing  with  (See  p.  246).  In  1898 
about  30  plants  were  self-fertilized;  they  yielded  a  poor 
harvest.  The  crop  raised  from  26  of  them  consisted  of 
about  2200  plants,  i.  e.,  about  90  per  seed  parent.  The 
hereditarv  values  for  each  of  these  are  arrans^ed  in  the 
following  list  in  groups,  as  before. 

%   SCINTILLANS  NUMBER  OF  MOTHER  PLANTS 

66—69  %  2 

71—74  %  2 

76—80  %  5 

81—85  %  6 

86—90  %  9 

92—93  %  2 

The  average  is  84  %  and  therefore  even  higher  than 
the  69  %  of  the  previous  generation. 

The  average  composition  of  the  whole  culture  from 
the  26  parent  plants  of  1898  was: 


0. 

scintillans 

84  % 

0. 

Lamarckiana 

13  % 

0. 

oblonga 

2  % 

0. 

lata 

1  % 

Oenothera  Scintillans.  391 

The  amount  of  0.  ohlonga  has  greatly  decreased, 
whilst  that  of  Lamarckiana  has  somewhat  increased  (see 
p.  246). 

In  the  summer  of  1899  I  again  selfed  a  whole  series 
of  plants  in  this  culture.  I  selected  these  from  the  off- 
spring of  two  plants  which  had  produced  respectively 
87  %  and  90  %  scintillans  and  seemed,  therefore  most 
likely  to  breed  true.  I  only  fertilized  scintillans  plants. 
The  yield,  however,  was  very  poor;  10  seed  parents  only 
giving  more  than  60  seedlings  each.  These  could  be 
recorded  in  June  and  showed  high  hereditary  coefficients : 


MOTHER 

NUMBER  OF  SEEDLINGS 

%    SCINTILLANS 

1 

146 

86 

2 

122 

91 

3 

113 

76 

4 

112 

92 

5 

98 

89 

6 

96 

87 

7 

77 

83 

8 

75 

80 

9 

74 

81 

10 

68 

74 

The  whole  crop  raised  from  the  seeds  of  the  29  plants 
gave: 

NUMBER  OF  SEEDLINGS  % 

O.  scintillans  1126  79 

O.  Lamarckiana  93  6 

O.  oblonga  209  15 

Total     1428 

These  figures  agree  almost  exactly  with  the  mean 
value  of  the  culture  in  the  previous  generation  in  spite 
of  the  fact  that  I  began  the  culture  with  two  seed  parents 
with  exceptionally  high  ^n/i^/7/a7Z.y-producing  capacity, 
viz.,  ^7  %  and  90  %,  and  irrespective  of  the  fact  that 


392   Origin  of  Each  Species  Considered  Separately. 

the  proportions  for  the  other  mutants  seem  to  have  been 
inverted. 

This  result  tends  to  prove  the  correctness  of  the 
conclusion,  suggested  above  (p.  389),  that  the  devia- 
tions from  the  mean  hereditary  coefficient  are  phenom- 
ena of  fluctuating  variability  and  have  nothing  to  do  with 
mutation. 

The  fifth  mutant  of  O.  scinfillans  from  which  I  was 
able  to  get  seed  arose  in  1898  from  the  /a/a-family  de- 
scribed on  page  285.  There  was  only  one  plant  which 
unlike  all  the  previous  ones  developed  a  stem  very  early 
and  flowered  in  the  first  summer.  It  was  self-fertilized 
in  a  bag,  set  little  seed  and  gave  rise  in  1899  to  148 
identifiable  plants  of  which  37  %  were  scintillans^ 

This  is  another  example  of  the  hereditary  coefficient 
exhibited  bv  two  of  the  three  other  mutants  which  were 
tested — a  particularly  interesting  case  because  the  origin 
of  this  scintiUans  was  quite  different  from  that  of  the 
others  and  the  plant  was  an  annual. 

I  shall  now  summarize  these  coefficients. 


SOURCE  YEAR  OF  MUTATION 


SCINTILLANS  PLANTS 

2nd  gen.  3rd  gen.     4th  gen. 

O.  lata                                  1888                      —  IS  % 
O.  lata                                  1898                    37  % 

O.  Lamarckiana                   1895                  34—36  %  40  % 
O.  Lamarckiana                   1896                    39  % 

O.  Lamarckiana                  1896                    69  %  84  %          79  % 

These  figures  seem  to  be  arranged  in  groups  of  15  %, 
34-40  %,  and  69-84  %.  It  would  obviously  be  very  im- 
portant to  determine  more  of  these  figures  in  the  case 
of  a  large  number  of  ^cm////a/w-mutants ;  if  this  were 
done  the  groups  will  probably  turn  out  to  be  more  vari- 

^  See  the  first  table  on  p.  245. 


Oenothera  Elliptica.  393 

able,  or  even  wholly  illusory.     Perhaps  we  might  even  get 
a  constant  race  of  scintillans. 


§  20.    OENOTHERA  ELLIPTICA. 

Almost  every  year  there  appear  amongst  my  plants 
isolated  individuals  with  very  narrow  leaves.  There 
are  three  types  of  such.  First  those  in  which  the  narrow- 
ness is  the  result  of  some  malformation.  Sometimes 
one  half  of  the  leaf  in  this  case  is  more  reduced  than  the 
other  and  the  leaf  is  consequently  more  or  less  deformed. 
Plants  of  this  kind  sooner  or  later  return  to  the  normal 
type  of  0.  Lamarckiana,  and  behave  afterwards  just 
like  this.  The  narrowness  is  presumably  in  this  case  a 
pathological  phenomenon ;  I  shall  not  deal  further  with  it. 

The  two  other  types  are  constant  and  maintain  the 
character  throughout  life.  One  of  the  forms  has  long 
leaves  which  are  broadest  in  the  middle  and  gradually 
taper  off  to  the  tip  and  to  the  stalk.  I  call  this  form  0. 
elliptica.  The  other,  a  much  rarer  form,  has  linear, 
almost  grasslike,  leaves  and  will  be  described  in  the  next 
section  under  the  name  of  O.  suhlinearis. 

The  seedlings  of  O.  elliptica  are  recognizable  at  a 
very  early  age  (Fig.  83  B,  to  be  compared  with  Figs. 
64-66,  pp.  325-326).  Its  leaves  have  long  petioles  and 
are  very  narrow,  seldom  attaining  a  breadth  of  more 
than  0.5-0.7  cm.  for  a  length  of  8-10  centimeters.  One 
result  of  this  is  that  they  assimilate  much  less  carbonic 
acid  than  0.  Lamar ckiana,  so  that  they  are  weak  and  very 
easily  overgrown  by  their  normal  neighbors.  But  even 
when  they  are  transplanted  early  and  treated  with  every 
possible  care  they  grow  very  slowly.  The  plant  shown  in 
Fig.  83  B  was  photographed  in  July. 


394   Origin  of  Each  Species  Considered  Separately. 

The  great  majority  of  the  new  mutants  of  this  species 
stayed  in  the  rosette  stage  their  first  year;  but  they  were 
so  dehcate  that  I   did  not  succeed  in  wintering  them. 


Fig.  83.  Oenothera  elliptica.  A,  twig  of  an  adult  plant, 
(1895)  ;  B,  a  seedling  of  1893;  C.  radical  leaf  of  a  full 
grown  rosette. 


Others  developed  stems  but  did  not  flower.  I  have  only 
seen  flowers  on  ten  plants  altogether  and  only  obtained 
seed  from  five  of  these. 


Oenothera  Elliptica. 


395 


j^r 


■f*!."^'. 


\ 


\ 


Even  when  they  flowered  the  plants  were  still  deli- 
cate: their  leaves  retained  the  long  narrow  shape  (Fig. 
83  ^).  The  plants  do  not  as  a  rule  attain  a  great  height 
but  are  profusely  branched  and  are  so  unlike  an  Oeno- 
thera Lamarckiana  that  they  do  not  look  as  if  they  could 
be  any  relation  to  it.  So  unlike,  indeed,  are  they  that  the 
seedlings  ran  the  risk  of  being  taken  for  weeds  and 
thrown  away.^ 

But  the  flowers  reveal  its 
kinship  with  O .Lamarckiana 
at  once.  They  are  large  and 
fine,  much  larger  indeed  for 
so  weak  a  species  than  our 
experience  of  O.  oblonga,  O. 
scintillans  and  others  would 
lead  us  to  expect.  They  have 
the  same  structure  as  those 
of  the  parent  species;  the 
stigma  extends  well  above 
the  anthers  and  so  cannot  be 
fertilized  without  the  help 
of  insects  or  of  the  experi- 
menter. The  shape  of  the 
petals  however  is  different,  as  will  be  made  sufficiently 
evident  by  a  comparison  of  Fig.  84  with  Fig.  42  on  page 
218.  The  petals  of  O.  Lamarckiana  are  broader  than 
long,  indented  at  the  tip  and  so  more  or  less  obcordate. 
In  the  open  flower  their  margins  overlap  so  that  a  closed 
cup  is  formed.     The  petals  of  0.  elliptica  are  elliptical ; 

^  This  circumstance  considerably  increases  the  work  in  my  ex- 
perimental garden.  Weeding  ought  only  be  done  by  assistants  who 
can  assign  individual  plants  to  their  species  and  can  be  trusted  to 
spare  unknown  forms.  For  the  rarer  a  mutant  is  the  more  likely  is 
it  to  be  taken  for  a  weed.  For  this  reason,  I  have  usually  done  this 
work  myself. 


Fig.  84.  Oenothera  elliptica.  An 
open  flower,  to  show  the 
rounded  tips  of  the  petals, 
(1895). 


396   Origin  of  Each  Species  Considered  Separately. 

their  greatest  breadth  is  about  their  middle  or  sHghtly 
above  this  and  they  are  rounded  at  the  tip.  They  are 
very  hke  the  autumn  flowers  of  0.  laevifolia.  (Fig.  59, 
p.  312),  only  that  they  have  this  shape  from  the  be- 
ginning of  the  flowering  period.  And  just  as  the  shape 
of  the  petals  in  laevifolia  in  autumn  may  be  ascribed  to 
the  diminished  supply  of  nutriment  at  that  time  of  the 
year,  so  there  is  very  probably  some  causal  relation  be- 
tween the  shape  of  the  petals  and  the  narrowness  of  the 
leaves  in  0.  elliptic  a. 

The  pollen  w^as  frequently  empty,  but  this  also  hap- 
pens occasionally  in  other  species  as  in  O.  scintillans  and 
even  in  O.  gigas.  It  is  quite  normal  for  numerous  species 
of  Oenothera  to  have  a  large  proportion  of  sterile  pollen, 
as  for  example  in  O.  biennis  L.  and  O.  niuricata  L.  The 
fruits  of  elliptica  were  small,  and  contained  little  seed. 

The  origin  of  0.  elliptica  has  alread}^  been  noted  in 
the  pedigrees  of  the  various  families  (Part  II,  §§1-7). 
Here  is  a  summary  of  these  cases : 

FAMILY  YEAR  NUMBER  OF  O.  ELLIPTICA 

O.  Lmnarckiana,  a  branch 

of  the  main  family,                    1895,  1896  8 

O.  laevifolia                         1889,  1891,  1893,  1894                   7 

O.  lata                                                   1900  1 

O.  lata                                               1890  2 

I  have  not  entered  the  occurrence  of  0.  elliptica  in 
the  pedigree  of  the  La/warc^fana- family  (p.  224)  ;  its 
occurrence  in  the  various  years  in  which  it  appeared  was 
as  follows : 

YEAR  NUMBER   OF   O.  ELLIPTICA 

2nd  Generation  1888  2 

3rd  "  1890  2 

6th  '•  1896  7 


Oenothera  Elliptica.  397 

O.  elliptica  occasionally  appeared  in  other  cultures. 
Here  are  some  examples. 

OENOTHERA  ELLIPTICA. 

INDIVIDUALS   THAT    HAVE    ORIGINATED   BY    MUTATION. 

NUMBER  OF  SEEDLINGS 


SOURCE  YEAR 


TOTAL      O.  ELLIPTICA 

3200  6 


O.  Lamarckiana  (subsidiary  cul-      j  1889, 1891, 
tures  in  the  laevifolia-f SLmily)        I  1893, 1894 

O.Lamarcktana{iTom.  O.sciniillans)       1898  1080  2 

O.oblonga                                                    1896  1680  1 

O.  Lamarckiana  X  O.  nanella                  1899  3815  1 

O.  Lamarckiana  X  O.  brevistylis             1898  290  1 

O.  Lamarckiana  X  O.  suaveolens  Desf.  1897  200  1 


Totals    10265  12 

This  is  a  proportion  of  about  1  in  a  thousand.  It 
appeared  in  similar  proportions  in  other  cultures.  Alto- 
gether rather  more  than  50  mutants  have  arisen. 

This  species  flowered  in  1890  (1),  1891  (1),  1895 
( 3 ) ,  1 896  ( 3 ) ,  1 897  ( 1 ) ,  that  is,  only  tentimes  altogether. 
I  obtained  seeds  from  the  three  plants  of  1895,  and  from 
those  of  1896  and  1899;  in  all  of  which  cases  self-fertili- 
zation had  taken  place  under  bags. 

The  first  plant  of  1895  set  seed  abundantly,  and  gave 
rise  to  some  hundreds  of  seedlings,  wdiich  grew  to  fine 
rosettes  but  proved  however  to  be  ordinary  Lamarckiana. 
Many  of  them  flowered  in  their  first  summer,  but  others 
passed  through  the  winter  as  rosettes. 

The  second  mutant  had  about  500  offspring;  one  of 
these  was  an  0.  elliptica  which  had  become  a  fine  rosette 
by  the  middle  of  August  but  was  then  killed  by  a  cater- 
pillar in  the  soil.  The  remaining  seedlings  were  normal 
Lamarckianas. 


398   Origin  of  Each  Species  Considered  Separately. 

The  third  plant  of  1895  set  little  seed  and  only  gave 
rise  to  27  seedlings  not  one  of  which  was  an  elliptica. 

The  mutant  of  1896  was  an  extraordinarily  beautiful 
plant  with  narrow  leaves  and  narrow  elliptical  petals,  and 
altogether  absolutely  unlike  an  ordinary  Oenothera.  Its 
fruits  were  long  and  thin  and  contained  but  few  fertile 
seeds.  32  seeds  germinated;  27  of  the  plants  they  gave 
rise  to  were  O.  Lamarckiana,  the  remaining  5  were  0. 
elliptica — that  is  about  15  %.  These  five  plants  devel- 
oped stems,  but  did  not  flower  till  November :  they  were 
exactly  like  their  parent.  Their  leaves  did  not  exceed 
2-3  cm.  in  breadth,  the  petals  were  elliptical  and  without 
the  emargination  at  the  tip.     They  did  not  set  seed. 

The  last  mutant  which  bore  seed  was  a  plant  which 
arose  in  1899  from  seed  of  0.  scintillans.  It  appeared 
in  the  culture  of  5850  rosettes  (p.  388)  which  gave  40  % 
O.  scintillans  in  the  third  generation.  This  culture  con- 
tained only  one  0.  elliptica,  which,  as  it  was  transplanted 
early,  grew  up  into  a  plant  which  branched  profusely 
and  flowered  freely  but  was  of  rather  low  growth.  Its 
leaves  were  very  narrow  but  its  flowers  relatively  large. 
The  breadth  of  the  petals  on  this  plant  was  highly  vari- 
able. Its  fruits  were  slender  and  contained  but  little  seed. 
Abut  100  seeds  germinated,  but  gave  rise  solely  to  ro- 
settes of  O.  Lamarckiana. 

To  sum  up:  the  hereditary  coefficient  for  O.  elliptica 
was  0  in  three  cases,  1  per  500  in  one  case,  and  about 
15  %  in  the  remaining  one.  The  first  three  plants  had 
only  a  few  hundred  offspring  between  them,  and  this  fact 
in  itself  may  be  sufficient  to  account  for  the  non-appear- 
ance of  cllipticas  amongst  them.  If  this  is  really  the  case 
the  last  two  mutants  (with  0.2-15  %)  may  provisionally 
be  regarded  as  representing  the  normal. 


Oenothera  Sublinearis. 


399 


§  21.    OENOTHERA  SUBLINEARIS. 

This  form  differs  from  the  last  named  chiefly  by  its 
grass-hke  leaves  which  are  very  narrow  and  of  equal 
breadth  along  their  whole  length  (Figs.  85  and  86).  The 
foliage  leaves  are  longer  and  markedly  narrower ;  the 


Fig.   85.     Oenothera  sublinearis.     Two   annual 
plants,  at  the  end  of  August  1900.     A,  with 
out,  and  B  with  flower  buds. 


Fig.  86.  Oeno- 
thera sublinearis 
A    radical    leaf, 

1895. 


foliage  on  the  stem  is  dense  and  not  scanty ;  the  fruits  are 
short,  and  not  slender  as  in  O.  ellipfiea.  Although  I  have 
had  very  few  examples  of  this  species  so  far,  it  is  evi- 


400   Origin  of  Each  Species  Considered  Separately. 

dently  a  genuine  well-characterized  type;  the  herbarium 
specimens  and  photographs  I  have  kept  of  the  first  that 
appeared  agree  perfectly  with  the  mutants  which  have 
arisen  since. 

The  flowers  presented  no  differences  from  those  of 
O.  elliptica.  They  are  the  same  size,  that  is,  are  some- 
what smaller  than  those  of  0.  Lamarckiana,  but  large 
when  the  weakness  of  the  species  is  taken  into  considera- 
tion. The  petals  are  not  obcordate  but  narrower  at  the 
extremity,  and  rounded  or  sometimes  even  pointed  at  the 
tip.     The  stamens  and  stigmas   resemble  those  of  the 

parent  species. 

^^^         ^^^^  Examples  of  0.  snblinearis  ap- 

i^^^l       ji^^^^k      peared  in  my  cultures  from  year  to 

\      WKKKU     year,    but    the   majority   of    them 

' '^  /    /  ^^y^       perished  as  young  rosettes.     Only 

^X^^y^  ^our  plants  grew  beyond  this  stage 

^  ^m  and  only  one  of  these  afforded  fer- 

Fig.  87;  Oeiiotherasub-     ^ile  seed,   which  when  sown   pro- 
linearis.    retals  with  a  .  ^ 

stamen,     July,     1896.      duced  the  new   form   in  the  pro- 

From  the   same  bien-       ^^^4.: ^r    m  «9/         t      ^.i  •  4. 

nial  plant  as  Fig.  86.      portion  of   10  %.^     In  this  respect 

it  falls  therefore  into  the  same  cat- 
egory as  O.  scintillans  and  0.  elliptica. 

The  history  and  fate  of  the  four  mutants  which  pro- 
duced stems  must  now  be  briefly  described.  I  shall  be- 
gin with  the  single  plant  which  set  seed. 

This  plant  arose  from  seed  of  the  Lamarckiana- 
family  which  had  been  sown  in  1895,  but  had  remained 
in  the  ground  for  a  year.  It  was  recognized  in  June 
1896  as  a  peculiar  form  and  transplanted  separately.  It 
was  biennial  and  flowered  in  1897  on  its  numerous  lat- 
eral branches  which  however  bore  only  a  few  flowers 
each.     The  whole  plant  was  short  and  stunted,  and  its 


Oenothera  Siihlinearis.  401 

flowers  were  relatively  large.  They  were  self- fertilized 
in  parchment  bags.  But  the  harvest  was  very  scanty. 
Only  31  seeds  germinated,  and  these  were  transplanted 
with  the  greatest  care  and  cultivated  further. 

The  composition  of  the  progeny  was  by  far  the  most 
varied  that  I  have  observed ;  there  occurred : 

19  0.  Lamarckiana  1    0.  alhlda 

3  0.  subline aris  3  0.  suhovata 

1   0.  lata  10.  gig  as 

1   O.  nanella  2  0.  ohlonga 

I  weeded  out  the  Lamarckianas  as  strong  rosettes  at 
the  end  of  June,  when  there  could  no  longer  be  any 
doubt  as  to  their  identity.  The  O.  snhlinearis  and  0. 
subovata  remained  in  the  rosette  stage  and  died  in  the 
winter.  All  the  remaining  plants  flowered,  some  in 
August  and  September,  and  some  (0.  gigas)  in  Novem- 
ber of  the  same  year.  Their  identity  with  plants  grown 
from  the  seed  of  mutants  of  the  same  name  was  fully 
established  especially  in  the  case  of  the  rarer  forms  0. 
albida  and  0.  gigas. 

This  extraordinary  richness  in  mutants  is  probably 
connected  in  some  way  with  the  smallness  of  the  harvest 
as  was  believed  to  be  the  case  in  the  experiment  described 
on  page  264.  This  highly  important  point  needs  further 
investigation. 

The  second  plant  belonged  likewise  to  the  Laniarc- 
kiana-fd.m\\y ;  it  appeared  in  1895  and  flowered  in  1896. 
One  of  its  first  year's  radical  leaves  is  shown  in  Fig.  86, 
two  of  the  petals  which  it  bore  in  1897  are  shown  in 
Fig.  87.  The  plant  was  pale  green  and  so  weak  that 
there  seemed  very  little  chance  of  its  surviving  the  win- 
ter.    But  it  flowered  rather  well :  there  were  about  a 


402   Origin  of  Each  Species  Considered  Separately. 

dozen  flowers  on  two  stems  which  arose  from  the  axils 
of  its  radical  leaves.  These  attained  a  height  of  about 
half  a  meter.  But  in  spite  of  all  the  trouble  I  took  I  got 
no  fertile  seed  from  it. 

The  third  mutant  arose  in  1900  in  the  first  Lata- 
family,  as  already  recorded  in  the  genealogical  table  on 
p.  285.  It  is  figured  in  Fig.  85  B.  It  was  planted  out  in 
June,  grew  well,  but  remained  short  and  did  not  branch. 
It  bore  large  flowers  and  small  fruits  and  was  cut  off  at 
the  end  of  August  to  be  photographed. 

The  fourth  mutant  (Fig.  85^)  arose  from  a  cross 
between  O.  rnbrinervis  and  O.  nanella,  which  was  made 
in  1899.  It  developed  an  unbranched  stem,  which  at- 
tained a  length  of  about  half  a  meter,  in  its  first  year, 
but  it  did  not  flower. 

D.  THE  STERILE  SPECIES. 
§  22.  OENOTHERA  LATA. 

One  of  the  most  difficult  questions  which  the  muta- 
tionist  has  to  answer  is  that  which  refers  to  the  nature 
of  the  fundamental  process,  involved  in  mutation  the 
visible  results  of  which  are  the  peculiarities  and  char- 
acters by  means  of  which  the  new  form  is  distinguished 
from  the  parent  species.  I  have  already  laid  stress  on 
the  fact,  which  has  not  escaped  the  notice  of  the  best 
workers  in  this  field,  that  elementary  species  are  not  dis- 
tinguished from  one  another  by  one  character  only,  as 
varieties  are,  but  by  almost  all  their  organs  and  charac- 
ters. This  is  not  only  true  of  the  elementary  species,  in 
a  state  of  nature,  which  have  been  described  by  Jordan^ 
Gandoger,  Thuret,  De  Bary,  Rosen  and  many  others 
but  also  of  those  which  have  arisen  in  my  cultures. 


Oenothera  Lata. 


403 


I  hold  that  all  the  new  characters  of  a  mutant  are 
manifestations  of  a  single  change  that  has  taken  place 
within  it.  Morphological  proof  of  this  thesis  can  as  yet 
hardly  be  produced,  but  physiologically  it  follows  of 
necessity,  in  my  opinion,  from  the  fact  that  these  char- 
acters are  always  associated  and,  so  far  as  our  experience 
goes,  cannot  be  separated. 


Fig.  88.     Oenothera  lata.    A  lateral  branch  at  the  end  of 
August  just  opening  its  first  flower. 

Oenothera  lata  is  perhaps  the  most  beautiful  example. 
I  have  already  described  the  characters  peculiar  to  it  in 
§  3  on  pages  239-243  (Fig.  46),  but  I  propose  now  to 
elaborate  that  description.     In  the  first  place  it  is  one  of 


404  Origin  of  Each  Species  Considered  Separately. 

the  commonest  mutants,  and  at  the  same  time  one  of  the 
most  easily  recognizable  in  its  early  stages.  It  appeared 
229  times  in  the  main  line  of  the  Lamar ckiana-id.m\\y 
(p.  224),  in  the  branch  family  171  times,  in  the  laevi- 
/o/m-family  9  times  and  very  frequently  in  other  cultures 
too.  I  have  cultivated  many  such  mutants  until  they 
flowered  and  set  seed ;  in  every  case  they  conformed  ex- 
actly to  a  common  type. 

No  separation  of  the  characters  of  the  species  has 
been  observed.  Oenothera  semilata  (§  17)  which  ap- 
peared at  first  to  be  an  instance  of  this,  turned  out  to  be 
a  distinct  form. 

The  characters  of  the  species  can  be  regarded  as 
distinct  "groups,"  better  in  the  case  of  O.  lata,  than  in 
the  case  of  any  other  species.  Each  ''group"  obviously 
constitutes  a  unit,  but  how  the  existence  of  the  separate 
''groups"  is  brought  about  by  the  same  cause  is  as  yet 
unknown.  Examples  of  these  "groups"  are,  the  form 
of  the  leaves,  the  thick  flower-buds,  the  lack  of  pollen, 
the  abnormal  growth  of  the  pistil,  and  the  short  fruits 
w^ith  relatively  few  seeds. 

Let  us  look  at  the  leaves;  they  are  crumpled,  and 
round  at  the  tip ;  the  edge  is  too  small  for  the  area  of  the 
leaf  which  is  therefore  much  bent.  The  bracts  are  much 
broader  at  the  base  than  they  are  in  the  parent  species. 
The  apices  of  the  large  branches  and  the  smaller  lateral 
branches  form  peculiar  little  rosettes.  A  complete  de- 
scription would  extend  over  a  whole  page  of  print  and 
need  many  figures.  (Fig.  89.)  Nevertheless  it  is  certain 
that  all  these  units  are  intimately  bound  up  with  each 
other  and  that  they  must  owe  their  existence  to  the  pres- 
ence of  a  single  factor. 

Perhaps  this  factor  is  the  abnormally  luxuriant  super- 


Oenothera  Lata. 


405 


ficial  growth  of  the  leaf  parenchyma  in  proportion  to 
that  of  the  nerves;  but  perhaps  we  must  seek  deeper 
for  it. 

It  is  not,  however,  easy  to  see  how  the  same  cause 
can  make  the  stigma  abnormal,  the  fruits  small  and  the 
pollen  sterile.    On  the  other  hand  if  we  suppose  that  each 


Fig.  89.  Oenothera  lata.  A,  a  radical  leaf.  B,  the  bract, 
from  the  axil  of  which  the  lowest  flower  arose.  C,  apex 
of  a  small  lateral  branch.  A',  B',  C,  the  corresponding 
parts  of  O.  Lamarckiana  diminished  the  same  amount. 

of  these  characters  is  due  to  a  distinct  cause  we  have  no 
means  of  accounting  for  the  fact  that  they  always  appear 
together  and  never  one  at  a  time :  for  this  clearly  could 
not  be  due  to  chance. 

I  imagine  that  the  cause  of  every  such  a  mutation 


406  Origin  of  Each  Species  Considered  Separately. 

is  a  single  one ;  though  its  real  nature  is  not  yet  apparent 
to  us.  But  this  much  is  clear,  that  it  is  not,  at  least  as  a 
rule,  manifested  as  a  single  quality.  And  in  this  respect 
a  mutant  differs  from  a  variety,  in  which  single  qualities 
like  color,  hairiness  and  so  forth  form  the  diagnostic 
character.  In  the  mutant  this  quality  can  only  be  mani- 
fested in  connection  with  the  older  characters  of  the 
plant;  and  the  total  expression  of  this  cause  must  there- 
fore depend  partly  on  the  older  characters  and  only 
partly  on  the  new  factor  itself. 

If  we  look  at  it  in  this  way  we  can  easily  imagine 
how  a  single  internal  change  can  bring  about  the  ab- 
normal development  of  the  leaf  parenchyma,  of  the  pollen 
cells  of  the  anthers,  of  the  petals,  the  fruits  and  the  stig- 
mas, and  in  this  way  produce  the  broad  crumpled  leaves, 
the  sterility  of  the  pollen,  the  thickness  of  the  buds  and 
the  abnormal  stigmas. 

This  is  of  course  only  an  idea.  I  mention  it  partly 
to  simplify  the  problem  and  partly  because  it  may  indi- 
cate the  lines  along  which  the  problem  may  be  dealt  with 
empirically.  In  order  to  make  my  position  clearer  I  will 
now  tentatively  indicate  the  parallel  which  exists  between 
this  idea  and  certain  phenomena  of  parasitism.  It  is 
generally  admitted  and,  indeed,  there  can  be  little  doubt 
that  the  wonderfully  definite  and  complicated  structure 
of  the  Cynipid-galls,  with  their  nutrient  tissue,  their 
stone-cells  and  their  spongy  tannin-containing  outer  par- 
enchyma^ whose  thickness  is  adapted  to  the  length  of 
the  ovipositors  of  parasites  and  Inquilinae,  cannot  be  the 
result  of  a  single  chemical  stimulus.  But  it  is  an  entirely 
different  matter  with  the  cases  of  virescence  since  these 

^  M.  W.  Beyerinck,  Bcobachtungen  i'lher  die  crsten  Entwiche- 
lungsphascn  ciniger  Cynipidcn-Gallen.  Verh.  d.  K.  Akad.  d.  Wet., 
Amsterdam,  1882. 


Oenothera  Lata.  407 

are  evidently  only  useful  to  the  parasites  in  quite  a  gen- 
eral way.  The  virescence  of  Lysiiuachia  vulgaris,  which 
is  occasioned  by  a  Phytoptns,  affords  perhaps  the  most 
beautiful  example  of  a  complete  series  of  transitions  from 
flowers  to  leafy  branches.^  This  change  is  obviously  the 
object  of  the  stimulus  given  by  the  Acarine  and  it  ob- 
viously does  not  matter  whether  the  number  of  the 
changed  petals  of  the  corolla  varies  or  not.  Neverthe- 
less these  and  other  monstrosities  accompanying  the  vi- 
rescence are  by  no  means  rare. 

The  case  of  the  virescence  on  the  galls  of  Anlax 
Hieracii,  in  the  flowerheads  of  Hieraciiim  viilgatwn,  H. 
tanhellatiim,  etc.,  which  have  been  studied  by  Treub,  is 
very  instructive.^  These  galls  are  usually  situated  in  the 
stems  far  away  from  the  flower,  but  in  rare  cases  they 
occur  in  the  flowerhead  itself.  When  this  happens  the 
flowers  are  affected  by  a  whole  series  of  the  most  re- 
markable malformations  which  begin  by  the  calyx  pro- 
ducing little  green  sepals.  These  changes  are  obviously 
of  no  use  to  the  Cynipids  which  live  inside  the  galls ; 
for  the  Aidax  larvae  grow  just  as  well  if  no  inflorescences 
are  borne  on  the  galls. 

Galls  not  rarely  evoke  monstrosities  of  this  kind, 
provided  of  course  that  the  potentiality  for  these  mon- 
strous growths  already  exists.  I  have  found,  for  ex- 
ample, a  stem  of  Hieraciimi  vulgatiim  which  was  normal 
below  the  gall  but,  above  it,  was  broadly  fasciated.  In 
the  summer  of  1887  I  saw  several  stems  of  Enpatoriiim 
cannahmum  bearing,  about  their  middle,  galls  of  Pter- 
ophorns  rnicrodactyhis :  below  these  the  leaves  were  green 

^  A.  B.  Frank,  PUanzcnkrankheitcn,  1880,  p.  691. 

^  M.  Treub,  Notice  sur  Vaigrette  des  Composccs.  a  propos  d'linc 
monstruosite  de  rHicracium  iimbcUatum,  Archives  Neerlandaises  d. 
sc.  phys.  et  nat.,  T.  VIII,  p.  i  and  Plate  I. 


408  Origin  of  Each  Species  Considered  Separately. 

but  above  them  they  were  variegated.  The  gall  stimulus, 
therefore,  does  not  exert  its  influence  only  on  those  qual- 
ities which  are  necessary  for  the  formation  of  the  galls, 
but  on  others  as  well. 

The  effect  of  a  single  mutation  on  the  most  diverse 
and  important,  as  well  as  on  subsidiary,  qualities  may 
be  of  a  similar  nature  as  that  of  a  gall  stimulus.  But  if 
it  is  difficult  to  discover  the  chemico-physiological  nature 
of  the  gall  stimulus ;  it  is  wellnigh  impossible  to  penetrate 
into  the  mystery  of  the  chemical  nature  of  a  primary 
mutation. 

Let  us  now  make  a  more  detailed  study  of  the  char- 
acters of  our  Oenothera  lata  and  let  us  begin  with  the 
stamens.  The  anatomical  structure  of  these  has  been  in- 
vestigated by  Prof.  J.  PoHL^  (Fig.  90),  partly  on  the 
plants  of  my  first  /a /a- family  (p.  285)  in  1894,  partly  on 
a  larger  culture  which  I  raised  in  that  year  from  the 
seeds  of  the  second  /a/a-family  (seeds  of  1889  and  of 
1890,  see  p.  288)  and  partly  on  isolated  new  mutations. 
The  structure  of  the  stamens  was  the  same  in  all  cases; 
and  was,  therefore,  independent  of  the  ancestry  of  the 
plant. 

Pollen  formation  takes  place  in  Oenothera  Lam  arc- 
kiana  and  O.  lata  in  the  ordinary  way ;  the  mother  cells 
enclosed  in  the  tapetum  each  divide  into  two  daughter 
cells  and  each  of  these  into  two  granddaughter  cells.  The 
loculus  increases  in  capacity  by  the  dissolution  of  the 
tapetum ;  and  the  further  development  of  the  pollen- 
grains  takes  place  in  the  fluid  which  now  surrounds  them. 
The  ripe  pollen  of  0.  Laniarckiana  consists  of  two  forms 

^Julius  Pohl,  Ueher  Variationsweite  von  Oenothera  Lamarc- 
kiuna;  Oesterr.  Botan.  Zeitschr.,  1895,  Nos.  5  and  6,  and  Plate  X. — 
See  also  R.  R.  Gates^  Pollen  Development  in  Hybrids  of  Oenothera 
lata;  in  Botanical  Gazette,  T.  43,  p.  81.     (Note  of  1908.) 


Oenothera  Lata. 


409 


of  grains,  about  70%  large  normal  grains,^  the  rest  being 
small  grains  poor  in  protoplasm.  The  pollen  of  0.  lata 
on  the  other  hand  consists  of  crumpled,  distorted  grains 
which  form  every  conceivable  transition  between  abso- 
lutely empty  sacks  and  apparently  normally  developed 
grains.  But  the  empty  ones  and  the  almost  empty  ones 
are  in  the  majority ;  the  apparently  well  developed  ones 
occurring  only  sparingly  amongst  them.  Moreover  the 
viscin  threads,  which  in  O.  Lamar ckiana  connect  all  the 
pollen-grains  together  so  that 
they  form  a  sticky  mass,  appear 
to  be  absent.  The  open  an- 
thers feel  dry  and  if  they  are 
touched  with  the  finger,  bits 
of  sticky  masses  of  pollen  do 
not  adhere  to  it. 

If  we  follow  the  develop- 
ment of  the  anthers  in  O.  lata 
in  a  series  of  buds  of  increas- 
ing size  we  find  that  develop- 
ment is  normal  up  to  about  the 
stage  of  tetrad  -  formation. 
Shortly  after  this  stage  disso- 
lution of  the  tapetum  takes 
place  and  there  are  found  floating  in  the  lumen,  besides 
apparently  normally  developed  tetrahedral  pollen  grains, 
some  quite  round,  others  invaginated  on  one  side. 

I  devoted  a  great  deal  of  time  in  1894  to  trying  to 
fertilize  O.  lata  with  its  own  pollen,  trusting  that  the 
few  apparently  good  pollen  grains  which  I  had  found 
would  be  able  to  effect  fertilization.     I  plastered  as  much 


Fig.  90.  Oenothera  lata. 
Transverse  section  of  an 
anther,  showing  the  large 
cells  of  the  tapetum.  After 
J,  PoHL,  Oesterr.  Bot.  Zeit- 
schrift,  1895,  Plate  10,  Fig. 
28. 


^Figured  by  Luerssen"  in  Pringsheim's  Jahrhiich.,  Vol.  VII,  pp. 
35-42,  and  Plate  IV,  Figs.  1-14  (Pollen  of  Oenothera  biennis). 


410  Origin  of  Each  Species  Considered  Separately. 

pollen  as  I  could  on  the  stigmas  of  a  few  flowers ;  but 
all  to  no  purpose.  Then,  as  it  was  difficult  to  liberate 
the  pollen  direct  from  the  anthers  on  to  the  stigma,  I 
teased  it  out  with  needles  on  to  a  glass  slide,  collected 
it  in  a  lump  and  transferred  it  direct  from  this  to  the 
stigma — but,  again,  all  to  no  purpose. 

After  this  I  pollinated  the  flowers,  without  castrating 
them,  with  the  pollen  of  a  remotely  related  plant,  be- 
longing in  fact  to  another  subgenus;  O.  odorata.^  I 
have  obtained  fertile  crosses  between  this  form  and  0. 
Lamarckiana,  O.  biennis  and  O.  miiricata.  It  ought, 
then,  to  be  able  to  fertilize  O.  lata  also;  but  my  attempts 
to  effect  this  were  practically  without  result  although 
I  pollinated  many  flowers  on  four  plants.  Only  a  single 
seed  germinated ;  and  this  produced  a  hybrid  plant.  This 
experiment  also  shows  that  self-fertilization  did  not 
occur. 

Besides  this  I  have  pollinated  castrated  and  non- 
castrated  flowers  of  O.  lata  with  the  pollen  of  O.  La- 
marckiana. I  have  also  tried  the  effect  of  putting  very 
little  Laniarckiana-poWcn  on  the  stigmas  of  uncastrated 
flowers  in  the  hope  that  perhaps  I  might  induce  self- 
fertilization  in  that  way.  All  these  experiments  gave 
exactly  the  same  result;  about  15-20%  of  the  seeds  gave 
O.  lata,  the  rest  0.  Lamarckiana. 

I  conclude  from  these  and  from  a  number  of  other 
experiments  that  the  pollen  of  O.  lata,  in  spite  of  the 
presence  of  occasional  apparently  good  grains,  is  never- 
theless absolutely  sterile.  One  result  of  the  establishment 
of  this  fact  is  that  the  castration  of  flowers  of  0.  lata  in 
hybridization  experiments  becomes  unnecessary. 

^  From  the  subgenus  Oenothera  (Euoenothera)  ;  whilst  O.  La- 
marckiana etc.  belong  to  the  subgenus  Onagra. 


Oenothera  Lata.  411 

If  there  had  been  evident  signs  of  the  existence  of 
pollen  in  individual  flowers  among  the  numerous  mutants 
and  their  offspring  which  I.  have  artificially  fertilized 
during  the  course  of  the  last  six  years,  I  must  certainly 
have  seen  it.     But"  this  has  never  been  my  lot.^ 

The  stigmas  have  also  been  figured  and  described 
by  PoHL.^  They  differ  from  those  of  0.  Lamarckiana 
by  their  tendency  to  be  confluent  with  one  another  and 
with  the  style.  Their  number  is  variable,  as  in  the  parent 
species,  where  4  is  the  normal ;  but  numbers  up  to  8  are 


Fig.  91.  Oenothera  lata.  Young  seedlings.  A,  showing 
the  cotyledons  and  the  two  first  leaves.  A',  natural  size. 
B,  with  7-8  leaves  (Vs)  two  months  old,  seen  from 
above.  The  tear  in  the  leaf  to  the  right  was  caused  by 
trying  to  bend  the  leaf  flat. 

not  rare.  As  result  of  the  concrescence  just  mentioned, 
there  arise  in  O.  lata  curious  hand-shaped  deformities. 
The  individual  fingers  of  these  hands  are  sometimes  free 
but  sometimes  fused  to  their  tips.  This  deformity  goes 
hand  in  hand  with  a  shortening  and  thickening  and  also 
with  a  crumpling  of  the  individual  stigmata.  The  capa- 
city for  taking  pollen  and  for  permitting  the  normal 
development  of  the  pollen  tube,  doe§  not,  however,  seem 
to  have  been  impaired  by  these  malformations. 

^  As  already  stated.  I  have  lately  raised  a  hybrid  of  0.  lata  which 
produces  some  fertile  pollen,  which  I  have  now  in  cultivation.  See 
Section  I,  §3.     (Note  of  1908.) 

^  Julius  Pohl,  /.  c.  p.  8  and  Fig.  27. 


412  Origin  of  Each  Species  Considered  Separately. 


The  fruits  are  short  and  thick  and  contain  Httle  seed. 
They  attain  scarcely  half  the  length  of  those  of  O.  La- 
mar ckiana  but  are  almost  as  stout  as  these. 

I  first  observed  the  above  mentioned  deviations  from 
the  type  of  O.  Lamarckiana  in  1887  on  the  very  first 
mutants,  as  far  as  they  could  be  discovered  without  mi- 


//  / 


Fig.  92.     Oenothera  lata.     Rosette  with  radical  leaves. 
Aged  about  3  months. 

croscopical  investigation ;  and  since  then  I  have  observed 
them  every  year  not  only  in  the  new  mutants  but  also 
in  their  progeny. 

Like  O.  Lamarckiana,  0.  lata  is  both  annual  and  bi- 
ennial. But  I  grow  it  as  an  annual  by  preference.  The 
first  two  leaves  which  appear  after  the  cotyledons  plainly 


Oenothera  Lata.  413 

reveal  the  identity  of  the  species  (Fig.  91  A).  The  tips 
of  the  leaves  are  rounded  and  not  pointed,  which  makes 
them  shorter.  About  a  month  after  germination  this 
character  is  so  clearly  expressed  that  I  choose  this  stage 
for  sorting  out  the  Lamarckianas  from  the  latas  in  the 
results  of  crosses.  This  form  of  the  leaf  is  maintained 
through  the  whole  life  of  the  rosette  (Fig.  92)  and  on 
the  lower  part  of  the  stem. 

The  wrinkling  and  distortion  which  so  detract  from 
the  beauty  of  the  leaves  in  O  Lamarckiana  are  much 
more  pronounced  in  0.  lata;  and  are  very  rarely  absent 
(Figs.  57  and  58,  pp.  310  and  311).  This  feature  may 
be  brought  about  by  the  relativel}^  small  margin  of  the 
leaf. 

On  the  whole,  the  abnormal  breadth  of  the  leaves  is 
maintained  up  the  stem  even  to  the  tops  of  the  inflores- 
cences and  branches  (Fig.  89).  But,  as  in  the  case  of 
Lamarckiana  itself,  the  leaves  become  gradually  more 
pointed  and  narrower  the  further  up  they  are.  Our 
figure  (Fig.  89  A,  A')  brings  this  out  very  clearly;  a 
fine  point  is  seen  on  the  otherwise  rounded  tip  of  the 
leaf.  If  we  look  at  the  lowest  leaf  which  bears  a  flower 
in  its  axil  or  an  immature  fruit  and  compare  it  with  a 
corresponding  leaf  on  a  Lamarckiana  plant  (Fig.  89 
B,  B'),  we  shall  find  that  the  relative  breadths  are  as  4  to 
3.  Higher  up  in  the  inflorescence  this  difference  in- 
creases ;  the  leaves,  from  whose  axils  the  flowers  which 
open  in  August  arise,  are  about  twice  as  broad  as  the 
corresponding  ones  in  the  parent  species.  And  if  we 
look  at  a  small  branch  from  above  it  looks  like  a  thick 
rosette  of  broad  leaves  (Fig.  89  C)  whereas  in  such  a 
view  of  Lamarckiana  the  leaves  are  reduced  to  small  and 
narrow  bracts  forming  a  kind  of  rosette  of  pointed  leaves. 


414  Origin  of  Each  Species  Considered  Separately. 

The   tops   of   the   flowering  branches   are   also   densely 
clothed  with  leaves  (Fig.  88). 

The  remarkable  thickness  of  the  buds  is  clearly 
brought  out  in  our  figures  (Fig.  46  on  p.  241).  The 
petals  have  not  sufficient  room  for  development  in  the 
thick  but  short  bud:  they  acquire  in  this  way  folds  and 
wrinkles  which,  even  when  the  flower  is  fully  open,  are 
never  completely  lost.  As  a  result  of  this  the  flowers 
are  always  rather  unattractive,  and  not  nearly  so  large 
and  bright  and  widely  opened  as  in  the  parent  species. 

The  stem  and  branches  in  O.  lata  are  weak,  often 
bent  downwards  with  the  tops  heavily  laden  and  usually 
needing  a  stake  to  prevent  their  falling  over.  The  lateral 
branches  flowering  in  September  are  frequently  seen  to 
hang  downwards;  thereby  heightening  the  characteristic 
appearance  of  the  species.  The  plants  do  not  as  a  rule 
attain  a  great  height;  seldom  more  than  half  that  of 
O.  Lamarckiana. 

With  all  these  peculiarities  O.  lata  is  perhaps  that  one 
of  the  new  species  which  differs  most  widely  from  the 
parent  form.  Moreover  it  can  be  recognized  in  its  ear- 
liest youth  no  less  certainly  than  easily  (Plate  IV  and 
Fig.  48  on  p.  280).  Doubtless  as  a  result  of  these  cir- 
cumstances it  Avas  the  first  mutant  which  I  noticed, 
and  the  only  one  wdiich  I  found  in  my  first  crop  of 
1887.  Since  that  date  it  has  appeared  every  year  as 
a  mutation.  And  as  it  can  be  seen  so  early  in  each  crop 
and  as,  therefore,  it  is  not  likely  that  it  will  be  overlooked 
to  any  large  extent,  the  proportions  in  which  it  appears 
may  be  regarded  as  established  on  a  sufficiently  firm 
basis  to  admit  of  a  comparison  between  the  small  differ- 
ences in  its  "mutation  coefficients"  (See  p.  338).  I 
found  that  these  numbers  vary  considerably,  often  sink- 


Oenothera  Lata.  415 

ing  to  0.01%  or  less,  or  mounting  to  2%  or  more.  Ex- 
ternal conditions  therefore  probably  affect  the  propor- 
tion in  which  O.  lata  arises  from  O.  Lainarckiana.  What 
these  conditions  are  is  a  subject  for  future  enquiry. 
Perhaps  they  exert  their  influence  only  during  the  ripen- 
ing of  the  seed  or  during  germination  (See  p.  263)  but 
probably  they  come  into  play  at  or  before  fertilization. 
In  order  to  give  some  idea  of  the  range  of  variations 
of  these  ''mutation  coefficients"  I  give  a  list  containing 
the  figures  which  have  already  been  given  (§§  2-7)  to- 
gether with  some  new  observations. 

INDIVIDUALS   OF   OENOTHERA   LATA   WHICH    HAVE  ARISEN 

BY  MUTATION. 


I.    FROM  O.LAMARCKIANA. 

LAMARCKIANA  FROM:  DATE  TOTAL 


SEEDLINGS 
O.  LATA  %  LATA 


Main  line  of  descent,  p.  224     1888-1890    25,000  8  0.03 

"     "         '•            "             1895         14,000  73  0.5 

"     "         "             "              1896           8,000  142  1.8 

"     "         "             "         1897-1899      3,500  6  0.2 

Lateral  branch,  p.  262                   1895         10,000  168  1.7 

An  annual  culture                          1897           4,132  11  0.3 

A  biennial  culture                          1897              164  8  5.0 

II.    FROM  CROSSES. 

O.Lam.x0.7ia7iella               1897-1899      8,283  22  0.3 

O.Lam.xO.gigas                        1899               100  2  2.0 

O.  Lam.  y^O.  biennis                    1900                80  1  1.0 

6>.Z,aw.  (from  crosses;  p.  300)     1896           4,600  7  0.2 

III.    FROM  OTHER  FAMILIES. 

O.Lam.irom  O.laevifolia           1889              400  3  0.8 

O.laevifolia                                     1894           1,500  2  0.1 

O.rubrifiervis                                 1894                96  2  2.0 

O.scintillans                             1896-1899      7,872  38  0.5 

If  we  examine  these  figures  closely  we  make  rather 
an  interesting  discovery.     A  high  figure   (5%)   is  only 


416  Origin  of  Each  Species  Considered  Separately. 

given  by  a  culture  of  strong  biennial  plants,  carried  out 
with  the  utmost  care  (1897).  Three  of  the  figures,  viz., 
1,  2,  2%  are  afforded  by  too  small  crops  to  be  of  any 
significance.  On  the  other  hand  the  cultures  of  1895  and 
1896  which  involved  8000,  10,000  and  14,000  plants 
respectively,  and  may  therefore  be  relied  on,  gave  0.5, 
1.7  and  1.8%  apiece.  These,  then,  are  the  most  reliable 
figures  with  which  the  rest,  with  the  exception  of  the 
first  named  (5%)  agree  very  well.  The  remaining  fig- 
ures, which  are  0.3—1—2—2—3—3—5—8  per  1000, 
were  either  obtained  in  earlier  years  or  in  special  cul- 
tures. 

In  the  whole  table  there  are  493  /a/a-mutants  amongst 
about  130,000  seedlings,  or  about  0.4%. 

§  23.   INCIPIENT  SPECIES. 

According  to  the  mutation  theory,  natural  selection 
chooses  between  species ;  some  are  eliminated  by  it,  others 
permitted  to  increase  and  multiply.  The  new  forms 
arising  from  a  single  parent  species  by  mutation  may  be 
very  numerous;  they  are  often  equally  well  equipped 
for  the  struggle  for  existence  being  distinguished  from 
one  another  by  characters  which  are  unimportant  in  this 
respect,  as  in  the  familiar  case  of  Draba  verna. 

But  should  there  have  arisen  from  Draba  verna,  be- 
sides the  elementary  species  now  existing,  others  less 
fitted  for  the  struggle  for  existence,  they  would  most 
certainly  have  been  eliminated  sooner  or  later.  And 
there  is  no  reason  for  supposing  that  elementary  species 
different  from  those  now  existing  have  not  been  pro- 
duced. 

I   have  seen  almost  every  year  in  my  cultures  of 


Incipient  Species.  417 

Oenothera  unfit  mutations  of  this  kind,  and  very  often 
in  considerable  numbers.  For  the  sake  of  completeness 
I  shall  describe  some  of  them  here.  They  are  not  dis- 
tinguished from  the  ''fit"  new  species  by  any  sharp  line 
of  demarcation,  and  perhaps  there  exist  amongst  them 
some  forms  from  which,  by  the  help  of  better  methods, 
it  may  some  day  become  possible  to  obtain  constant  types. 

They  are  the  beginnings  of  new  species  from  which, 
for  one  reason  or  another,  I  have  not  succeeded  in  ob- 
taining the  species  themselves.  For  example  it  was  only 
after  a  series  of  the  most  laborious  experiments  which 
extended  over  about  6  years  that  I  was  able  to  get  O. 
alhida  to  flower  and  set  seed  (§  15,  p.  349).  I  shall 
therefore  refer  to  these  forms  as  "incipient  species."^ 

My  incipient  species  were  more  or  less  aberrant  types 
and  exhibited  few  points  of  resemblance  with  the  new 
species  hitherto  described.  Of  late  years  I  have  devoted 
much  energy  to  their  cultivation,  but  with  varying  results. 

Many  of  them  died  as  young  rosettes;  others  formed 
fine  thick  clusters  of  root-leaves,  but  developed  no  stem. 
Some  I  was  able  to  bring  through  the  winter,  others  per- 
ished in  their  first  year.  Many  of  them  flowered,  in 
some  cases  as  early  as  August,  in  others  not  till  autumn. 
If  the  latter  happens  there  is  no  prospect  in  our  climate 
of  ripening  seed ;  when  the  former  was  the  case  I  always 
enclosed  the  flowers  in  parchment  bags  in  order  to  insure 
self-fertilization.  But  as  the  pollen  was  usually  sterile 
the  operation  was  commonly  fruitless.  I  then  tried  using 
the  pollen  of  0.  Lainarckimia  or  that  of  some  other  new 
species  but  with  no  better  success;  the  ovaries  seemed 
incapable  of  being  fertilized. 

Sterility  is  well  known  to  be  a  highly  variable  char- 

^  Ebauches  d'espcces,  of  some  French  authors. 


418  Origin  of  Each  Species  Considered  Separately. 

acter.  It  certainly  is  in  the  Oenotheras.  The  older 
species  0.  biennis,  0.  muricata  and  0.  Lamarckiana  al- 
ways produce,  so  far  as  we  know,  a  pollen  of  which 
some  part,  often  as  much  as  one-third,  consists  of  sterile 
grains.  It  would  be  very  useful  if  some  one  would  de- 
termine the  degree  of  this  fertility;  it  would  without 
doubt  follow  Quetelet's  law  of  fluctuating  variability 
and  would  probably  exhibit  also  partial  variability  in  a 
high  degree — since  the  percentage  of  sterile  grains  would 
be  likely  to  be  high  on  weak  lateral  branches.^  Sterile 
or  almost  sterile  individuals  may  therefore  appear  from 
time  to  time.  For  example  I  once  found  a  plant  of  Oeno- 
thera gig  as,  which,  in  spite  of  repeated  attempts  to  fer- 
tilize it  with  its  own  pollen,  set  no  seed.  And  Oenothera 
hrevistylis  is  much  more  often  than  not  absolutely  sterile, 
in  spite  of  the  full  development  of  its  pollen;  and  this 
sterility  is  closely  correlated  with  the  individual  varia- 
bility in  the  size  of  the  fruits. 

It  may  happen  that  a  new  species  absolutely  lacks 
pollen,  as  we  have  seen  to  be  the  case  with  O.  lata.  But 
it  does  not  follow  from  that,  that  every  new  form  that 
arises,  if  we  find  it  first  as  a  sterite  plant,  must,  when 
it  arises  once  more,  be  sterile  again. 

The  incipient  species  in  my  cultures  were  as  a  rule 
represented  by  solitary  individuals.  In  rarer  cases  the 
new  form  was  represented  in  the  same  crop  by  two  or 
three  seedlings;  or  was  repeated  in  succeeding  years.  If 
nothing  more  than  rosettes  of  radical  leaves  were  pro- 
duced, absolute  certainty  as  to  the  identity  of  the  type 
was  of  course  out  of  the  question ;  but  it  is  always  better 
ni  cases  like  these  to  unite  those  which  apparently  belong 

^  See  amongst  others  A.  Jencic,  Untcrsuchiingcn  i'lher  den  Pol- 
len hybridcr  Pftanzen,  Oesterr.  Bot.  Zeitschr.,  T.  50,  1900. 


Incipient  Species.  419 

together  than  to  multiply  new  types  indefinitely.  For 
these  unsuccessful  incipient  species  have  hardly  any  fur- 
ther signification  than  that  of  supporting  the  thesis  of 
indiscriminate  mutability. 

This  is  my  chief  reason  for  describing  here  in  some 
detail  a  few  such  incipient  species.  For  this  purpose  I 
select  three  of  those  which  I  have  noticed,  and  shall  call 
them  for  the  sake  of  convenience  by  ordin- 
ary specific  names.  They  are  O.  spatJiu- 
lata,  of  which  I  obtained  only  rosettes  of 
radical  leaves,  O.  stibovafa  which  flowered 
several  times,  but  was  always  sterile,  and 
O.  fatna  which  though  it  branched  freely 
has  produced  practically  no  flowers  so  far. 

Besides  these  three  types  there  was  a 
whole  series  of  other  forms  which  do  not 
seem  to  me  to  be  worth  either  naming  or 
describing.^ 

Of  0.  spathidata  I  obtained  two  ro- 
settes of  root-leaves  in  the  laevifolia-ia.m- 
ily  in  1889,  (p.  273)  ;  seven  rosettes  in 
1890  in  the  main  pedigree  of  the  Lauiarc- 
kiana-f am'ily;  and  one  in  a  lateral  branch  Fig- 93-  Oow- 
of  this  famny  m  1895  (p.  ZoZ).  lata.    A  rad- 

Repeated  appearance  in  different  and  ^  rlt^dyp 
mutually  independent  families  is  thus  es- 
tablished in  the  case  of  this  rare  new  species.  The  plants 
of  1890  were  fine  strong  rosettes  about  the  end  of  June: 
they  grew  healthily  through  the  whole  summer  but  died 
in  the  winter  without  having  developed  a  stem.  I  have 
kept  some  of  their  leaves  and  photographed  them  (Fig. 

^  Some  of  my  new  species  have  not  arisen  from  the  pure  stock  of 
O.  Lamarckiana  but  have  arisen  from  crossed  seeds  of  various  an- 
cestries.    Both  sterile  and  fertile  forms  have  arisen  in  this  way. 


420  Origin  of  Each  Species  Considered  Separately. 


93).  The  petiole  was  very  long,  gradually  merging  into 
the  blade  of  the  leaf;  the  latter  attaining  its  greatest 
breadth  near  its  rounded  apex. 

Another  mutant  with  similar  leaves 
flowered  in  the  same  summer;  it  had 
little  flowers  and  empty  anthers ;  but  I 
was  not  sure  whether  it  belonged  to  the 
same  type. 

I  gave  the  name  0.  fatna  to  a  plant 
which  arose  in  1896  from  the  Lamar c- 
kiana-idiXmly :  it  proved  a  biennial  and 
branched  profusely  in  1897.  It  bore 
numerous  inflorescences  with  green 
bracts,  but  no  flowers  (Fig.  94). 

In  the  summer  of  1896  I  had  isolated 
the  rosette  as  a  new  form;  the  leaves 
were  oval  and  obviously  different  from 
those  of  0.  Lamarckiana.  It  grew  vig- 
orously in  the  second  year,  attained  a 
height  of  about  a  meter,  produced  more 
branches  than  any  other  form  I  have 
seen  and  developed  the  most  extraordi- 
nary profusion  of  inflorescences.  It  was 
not  until  late  in  the  autumn  that  it  began 
to  develop  normal  flowerbuds,  too  late 
for  them  to  open. 

I  have  observed  isolated  examples 
of  similar  plants  on  other  rare  occasions. 
My  last  example  is  Oenothera  siib- 
ovata  which  first  appeared  in  1889;  and, 
afterwards,  as  isolated  examples  in  various  cultures, 
from  time  to  time.  Four  of  these  mutants  have  flowered ; 
the  rest  died  in  the  rosette  stage.    • 


Fig.  94.  Oeno- 
thera fatua.  A 
branch  in  au- 
tumn with  nu- 
merous flower- 
less  bracts. 


Incipient  Species. 


421 


Fig.  95  is  a  photograph,  taken  in  the  same  way  as 
those  already  given  for  other  mutations,  of  a  group  of 
young  plants  which  were  raised  from  the  seeds  of  Oeno- 
thera lata  fertilized  by  0.  Lamarckiana,  and  were  planted 
out  in  early  spring,  in  rows,  in  boxes  containing  good 


Fig.  95.  A  mutation  in  the  /ato-family.  From  a  photograph 
taken  on  the  25th  of  May  1900.  In  the  right  column 
there  can  be  seen  at  the  top  O.  alhida,  in  the  middle  O. 
lata,  and  at  the  bottom  O.  albida  again.  In  the  second 
column  O.  Lamarckiana,  O.  oblonga  (in  the  middle)  and 
O.  Lamarckiana.  In  the  third  row  O.  lata  (below),  O. 
oblonga,  and  O.  subovata  (at  the  top,  very  small).  In 
the  left  row  three  O.  lata,  and  in  the  middle,  the  largest 
rosette,  O.  Lamarckiana.  The  O.  lata  and  O.  Lamarck- 
iana are  like  the  two  parents,  the  rest  have  all  arisen  as 
mutations. 


soil.  It  shows  some  of  the  mutations  which  arose  from 
the  main  stem  of  the  /a/a-family  (as  given  in  detail  on 
page  285),  and  happens  to  be  a  group  in  which  many 
new  forms  are  growing  close  together.    The  figure  shows 


422  Origin  of  Each  Species  Considered  Separately. 

besides  0.  lata  and  O.  Laniarckiana  two  examples  of  O. 
albida,  (to  the  right),  recognizable  by  their  small  narrow 
leaves,  and  two  of  O.  oblong  a  (in  the  middle)  which 
can  hardly  be  distinguished  from  the  surrounding  ex- 
amples of  the  parent  species  in  the  picture.  The  major- 
ity of  the  /a/a-plants  photographed  flowered  afterwards. 
The  albidas  and  oblongas  grew  as  far  as  the  rosette 
stage,  but  died  in  the  course  of  the  summer.  The  La- 
marckianas  were  not  planted  out. 

The  O.  subovata  (the  second  from  the  left  in  the 
top  row)  was  noticeable  very  soon  after  transplanting 
by  the  fact  that  it  remained  very  small  whilst  the  other 
plants  grew  vigorously.  Its  leaves  were  almost  orbicular 
and  were  shortly  petiolate.  It  was  planted  out  at  the 
end  of  April  in  a  separate  bed  with  the  other  mutants, 
and  grew  up  to  a  strong  full  rosette  with  numerous  ovate 
leaves  with  long  petioles  which  distinguished  it  at  once 
from  all  the  other  plants  in  the  same  bed.  It  died  in  the 
autumn. 

The  two  other  examples  of  0.  subovata  (mentioned 
on  page  285)  died  in  the  latter  part  of  the  summer 
after  they  had  formed  thick  rosettes  similar  to  those  al- 
ready described  (see  also  Fig.  48  on  page  280). 

I  had,  before  this,  observed  one  or  two  instances  of 
rosettes  with  the  same  form  of  leaf  and  of  the  same 
general  appearance.  For  example  in  1895  I  observed 
seven  of  them  amongst  14,000  seedlings  of  the  main 
trunk  of  the  Lainarckiana-isLmily,  that  is  to  say  1  per 
2000  (p.  224).  They  survived  the  autumn,  but  not  the 
winter.  Then  there  were  the  three  mutants  (mentioned 
on  page  401)  which  arose  in  1898,  from  the  seeds  of  O. 
snblinearis  and  two  others  which  arose  from  0.  scintil- 


Incipient  Species. 


423 


lans.     And  last  of  all,  two  rosettes  from  seeds  of  Oeno- 
thera lata  fertilized  by  O.  biennis. 

I  obtained  altogether  four  flowering  plants  of  O.  siib- 
ovata,  one  in  1889  and  1895,  and  two  in  1899.  The 
former  arose  from  Lamarck- 
iana-SQcds,  was  annual,  freely 
branched  but  dwarfed.  It  de- 
veloped not  only  a  main  stem, 
but  lateral  ones  from  the  axils 
of  its  radical  leaves.  Only  a 
single  one  of  these  latter  bore 
normal  flowers  like  the  parent 
species.  The  other  lateral 
branches  and  the  main  stem 
however  were  quite  sterile.  In- 
stead of  flowers  in  the  axils  of 
the  leaves  there  were  little  green 
leafy  shoots  (Fig.  96)  which 
gave  the  plants  a  most  singular 
appearance.^ 

The  mutant  of  1895  arose 
from  the  Larnarckiana-isimily 
and  flowered  in  August  of  its 
first  year.  The  flowers  were  of 
the  same  form  as  those  of  the 
parent  species ;  but,  in  corre- 
spondence with  the  greater  deli- 
cacy of  the  plant,  smaller.  Later 
on,  however,  it  became  stronger  and  the  flowers  which 
were  borne  on  its  lateral  branches  at  the  end  of  Sep- 
tember were  quite  as  large  as  those  of  Laiiiarckiana. 

*  This  foliation  was  due  to  internal  causes  and  not  a  pathological 
virescence  like  that  which  may  be  brought  about  by  parasites  (Pliy- 
toptus,  plant-lice,  etc.).     I  have  occasionally  seen  examples  of  this 


Fig.  96.  Oenothera  sub- 
ovata.  A  barren  stem, 
1889. 


424  Origin  of  Each  Species  Considered  Separately. 

The  two  snhovata-y\2ints>  of  1899  belonged  to  the 
/a/a-family.  One  arose  from  lata  crossed  by  O.  nanella, 
the  other  from  lata  crossed  by  O.  Lamarckiana.  Both 
were  recognized  while  young  plants;  they  developed 
stems  and  flowered  freely.  The  first  was  weak  and  had 
relatively  small  flowers;  the  second  was  strong  and  bore 
flowers  as  fine  as  those  of  0.  Lamarckiana.  Both  were 
absolutely  sterile,  at  first  I  fertilized  them  with  their  own 
pollen  and  later  with  foreign  pollen,  but  in  both  cases 
without  result. 

But  I  regard  it  as  extremely  probable  that  I  shall 
some  day  succeed  in  getting  a  siihovata  that  will  bear 
seed.  And  if  siihovata',  why  not  other  forms  which  have 
not  been  detected,  or  even  have  not  yet  arisen  in  my 
cultures  ? 

latter  in  my  O^wof/i^ra-plants  (Botan.  Jaarhoek;  Gent,  1896,  p.  88). 
But  the  effects  of  it,  especially  the  actual  virescence  of  the  flowers 
themselves  bore  no  resemblance  to  the  peculiarities  of  the  plants 
described  above. 


III.    THE  SYSTEMATIC  VALUE  OF  THE  NEW 

SPECIES. 

§  24.   THE  NATURE  OF  THE  BOUNDARIES  BETWEEN 

RELATED  SPECIES. 

It  follows  directly  from  the  doctrine  of  mutation 
that  the  species  which  arise  by  mutation  are  as  sharply 
distinguished  from  one  another  as  are  neighboring  spe- 
cies of  recognized  systematic  value. 

The  previous  chapter  has  shown  us  that  new  species 
are,  as  a  rule,  from  the  very  beginning  as  constant  as 
other  species.  This  constancy  is  manifested  in  two  ways. 
In  the  first  place  the  various  individuals  of  the  new  spe- 
cies are  absolutely  alike  in  all  their  essential  features: 
and  this  is  true  not  only  of  the  offspring  of  new  muta- 
tions and  of  others  which  arise  from  the  same  parents, 
but  also  of  the  hosts  of  mutations  which  have  arisen 
from  widely  separated  and  independent  families  of  the 
same  parent  species.  In  the  second  place  they  come  true 
to  seed,  they  do  not  revert  to  the  parent  form.  If  the 
latter  character  is  absent  as  in  the  case  of  Oenothera 
scintillans  the  new  form  cannot  be  capable  of  existence 
in  nature  and  therefore  cannot  be  compared  with  true 
wild  species. 

The  object  of  the  present  chapter  is  to  show  that  the 
characters  of  the  new  species  which  have  arisen  in  the 


426       The  Systematic  Value  of  the  New  Species, 

genus  Oenothera  possess  the  same  systematic  value  as 
those  which  distinguish  the  species  of  Linnaeus  and 
later  systematists.  I  shall  confine  myself  to  the  nearest  rel- 
atives of  0.  Lamarckiana,  that  is  to  say,  to  the  subgenus 
Onagra.  In  this  way  I  shall  have  the  advantage  of  deal- 
ing with  very  well  known  forms  (0.  biennis  L.,  0.  muri- 
cata  L.,  0.  suaveolens  Desf.,  etc.)  and  of  using  them 
as  subjects  of  comparison.  The  new  species  differ  in 
some  respects  as  much,  in  others  more,  in  yet  others 
less  from  one  another  and  from  the  parent  species  than 
these  recognized  forms  do  amongst  themselves. 

And  first  I  must  emphasize  two  things  which  make 
the  treatment  of  this  subject  a  difficult  matter.  I  mean, 
our  present  wholly  insufficient  knowledge  of  the  units 
of  which  the  characters  of  organisms  are  built  up,  and 
secondly  the  phenomenon  of  transgressive  variability.^ 

I  believe  that  each  new  mutation  is  brought  about 
by  a  single  new  quality  (see  page  403).  This  inner  or 
primary  quality  then  comes  in  contact  with  the  qualities 
which  are  already  present  in  the  various  organs  and  it 
is  this  interaction  to  which  its  particular  external  mani- 
festation is  due.  The  nature  of  the  outward  and  visible 
form  therefore  depends  only  partly  on  the  mutation  but 
partly  also  on  the  characters  already  existing  in  the 
organism.  Or,  in  other  words,  the  new  species  is  marked 
not  as  a  rule  by  a  single  new  peculiarity  but  by  the  trans- 
formation of  many  or  all  of  its  organs,  more  or  less. 

So  long  as  we  do  not  know  the  single  causes  in  ques- 
tion we  must  compare  these  visible  transformations  in 
new  mutations  with  the  visible  dififerences  between  old 
established  species. 

Transgressive  variability  is  one  of  the  main  supports 

*  See  page  56,  and  the  following  section. 


The  Boundaries  Betzveen  Related  Species.       Ml 

of  the  current  theory  of  selection.  It  makes  it  possible 
to  pick  out  series  of  individuals  which  belong  to  related 
but  different  species  and  (being  careful  to  choose  suit- 
able characters)  to  arrange  them  in  such  a  way  that  they 
form  a  perfectly  continuous  series  from  one  end  to  the 
other.  If  no  gaps  have  been  left  in  such  groups  by  the 
death  of  species  or  if  there  are  sufficient  species  left, 
perfectly  continuous  series  of  this  kind  can  be  arranged 
of  almost  any  desired  length. 

But,  as  a  rule,  this  can  only  be  done  by  dealing  with 
single  characters  and  by  not  being  particular  about  the 
number  of  individuals  which  go  to  form  the  successive 
steps  in  the  series. 

An  example  will  make  my  meaning  clear.  Oenothera 
Lamarckiana  differs  from  0.  biennis  by  the  beauty  and 
size  of  its  flowers.  The  two  species  can  be  distinguished 
at  a  great  distance.  The  petals  of  the  former  are  twice 
as  long  as  those  of  the  latter.  But  in  both  species  the 
leno^th  is  variable  and  follows  Ouetelet's  law  of  indi- 
vidual  variability,  being  in  a  high  degree  dependent  on 
nutrition.  Petal-length  also  exhibits  partial  variability 
and  is  especially  low  at  the  end  of  the  flowering  period 
when  the  plant  is  exhausted  by  bearing  seed.  The  small- 
est flowers  are  found  on  the  main  stems  of  plants  which 
are  nearly  over,  on  small  lateral  branches  or  on  indi- 
vidually weak  plants :  the  largest  on  well  nourished  plants 
just  beginning  to  flower,  or  on  vigorous  lateral  branches 
of  large  plants  which  through  some  accident  or  other 
have  lost  their  main  stem.  This  is  true  both  of  plants  in 
the  field  and  of  those  in  the  garden. 

If  now  we  choose  the  largest  flowers  of  0.  biennis 
and  the  smallest  of  0.  Lamarckiana,  we  shall  find  tiiat 


428      The  Systematic  Value  of  the  New  Species. 

this  character  of  petal  length  overlaps  in  the  two  cases. ^ 
For  in  these  extreme  cases  the  flowers  of  biennis  are 
actually  larger  than  those  of  Lamarckiana.^ 

If  we  have  collected  a  number  of  flowers  including 
such  extremes,  it  is  obviously  an  easy  matter  to  arrange 
an  unbroken  series  with  the  smallest  of  biennis  at  one 
end  and  the  largest  of  Lamarckiana  at  the  other.  The 
limits  between  the  two  species  cannot  be  detected  in  such 
series  even  by  the  practised  eye.  And  yet  0.  bie finis  and 
O.  Lamarckiana  never  merge  into  one  another. 

If  we  wish  to  extend  the  series  we  can  do  so  by  adding 
the  small-flowered  0.  miiricata  to  it  in  exactly  the  same 
way.*^  And,  if  we  leave  relationship  out  of  account,  we 
could  extend  continuously  down  to  Oenothera  mimiti- 
flora  with  its  flower  no  longer  than  a  millimeter.  Such 
series  can  be  arranged  for  almost  any  character  in  the 
vegetable  kingdom  and  in  infinite  variety.^  They  con- 
fuse the  limits  drawn  between  related  species  as  far  as 
the  several  characters  are  concerned. 

If,  in  the  classification  of  animals  and  plants,  we  fix 
our  attention  on  a  single  character  we  shall  always  en- 
counter long  unbroken  series  of  this  kind.  The  shells 
of  snails  and  the  wings  of  butterflies  are  examples.     It 

*  That  this  must  generally  be  the  case  may  be  derived  from  the 
law  of  variability.  Imagine  two  curves  of  variation  drawn  on  the 
same  abscissa.  The  greater  the  number  of  individuals  included  the 
further  will  the  limits  of  the  curves  extend  until  they,  first,  touch  and 
ultimately  overlap.  It  is  further  obvious  that  the  likelihood  of  this 
happening,  even  with  a  small  number  of  individuals  depends  directly 
on  the  closeness  of  the  tops  of  the  curves  (the  mean  values  of  the 
characters)  and  on  the  amplitude  of  the  curve,  or  the  degree  of  var- 
iabihty  (Q). 

^  Examples  in  the  following  section. 

^  See  the  following  section. 

*  For  example  the  narrowest  leaves  of  Typha  latifolia  are  nar- 
rower than  the  broadest  leaves  of  T.  angustifolia. 


The  Boundaries  Between  Related  Species.       429 

is  only  when  we  compare  other  characters  as  well  that 
we  can  distinguish  the  individual  species. 

The  object  of  exact  inquiry  should  be  first  to  collect 
as  many  of  these  continuous  series  as  possible ;  but  second 
to  anah^ze  them  into  their  component  units. 

This  analysis  can  be  effected  both  by  the  statistical 
and  by  the  experimental  method.  Let  us  examine  the 
former  first. 

A  transgression  of  the  limits  is  only  exhibited  by 
isolated  and  relatively  few  individuals;  the  vast  majority 
belong  to  the  mean  type  of  the  species.  Therefore  if  we 
take  care  not  to  be  too  much  on  the  lookout  for  transi- 
tional forms,  or  even,  if  we  try  to  make  our  measure- 
ments as  numerous  as  possible,  the  separate  curves  will 
become  discernible.  The  result  will  be  exactly  that  which 
we  got  from  an  investigation  of  the  Oenothera  flowers, 
namely  curves  with  numerous  apices,  such  as  those  with 
which  the  work  of  Bateson^  Ludwig  and  others  has 
made  us  familiar.  Each  apex  indicates  a  group  of  indi- 
viduals which  belong  together,  to  a  type,  or  even  to  an 
elementary  species. 

Transitional  forms  can  then  be  recognized  imme- 
diately by  their  rarity.  It  becomes  obvious  that  the 
transitions  are  only  apparent  and  that  no  real  continuity 
between  the  different  centers  of  variation  exists.  These 
curves  show  no  more  than  that  the  edges  of  neighboring 
curves  on  the  same  abscissa  may  overlap. 

The  simplest  way  of  making  the  experimental  method 
clear  is  to  take  the  case  of  the  Oenothera  flowers  again. 
We  collect  the  seeds  from  the  fruits  of  two  flowers  of 
equal  size  of  which  one  is  one  of  the  largest  flowers  of 
Ocn.  biennis,  the  other  one  of  the  smallest  of  Ocn.  La- 
marckiana.   There  can  be  no  doubt  what  the  plants  raised 


430       The  Systematic  Value  of  the  New  Species. 

from  these  seeds  will  be  like.  The  result  can  indeed  be 
predicted  pretty  accurately  by  means  of  the  law  of  re- 
gression (see  pp.  72>,  120  et  seq.).  The  seeds  of  the 
biennis-^ov^^r  will  give  plants  whose  flowers  revert  to 
the  mean  of  the  type  of  hicnnis ;  the  seedlings  of  the  La- 
marckiana-flower  will  revert  to  the  normal  of  that  spe- 
cies. 

In  other  words :  if  we  are  in  doubt  as  to  the  nature 
of  individuals  which  stand  at  the  boundary  between  re- 
lated species,  the  offspring  produced  after  the  self-fertili- 
zation of  the  individuals  in  question  will  settle  the  diffi- 
culty. Two  plants  which  are  absolutely  identical  in  re- 
spect of  any  particular  character  may  be  proved  by  their 
progeny  to  be  fundamentally  different.  And  if,  as  often 
happens,  two  related  groups  only  differ  in  a  single  char- 
acter their  extreme  variants  may  be  indistinguishable. 
Yet  their  seed  will  prove  them  to  be  intrinsically  differ- 
ent. 

The  study  of  the  limits  of  species  is  by  no  means 
solely  a  descriptive  one.  Classifications  based  on  no  more 
than  an  examination  of  a  series  of  forms  have  no  more 
than  a  transitory  value.  ^  Statistical  methods^  will  re- 
veal where  the  boundaries  are :  experimental  methods 
must  be  called  in  to  decide  in  individual  cases. 

§  25.    TRANSGRESSIVE  VARIABILITY. 

The  general  conclusions  arrived  at  in  the  foregoing 
section  may  now  be  illustrated  by  numerical  data.  The 
determination  of  the  nature  of  the  limits  between  related 
species  is  one  of  the  most  difficult  parts  of  the  task  of  the 

^  De  Candolle,  La  Phytographie,  p.  80 

^  C.  B.  Davenport,  Statistical  Methods  with  Special  Reference  to 
Biological  Variation. 


Transgrcssive  Variability.  431 

systematist.  The  vast  majority  of  systematic  species 
are  made  and  described  on  a  few  specimens;  and  where 
large  numbers  of  individuals  have  been  available  the  in- 
vestigator has  contented  himself  with  the  general  im- 
pression they  produce  on  him.  The  result  of  this  is 
that  we  have  a  knowledge  of  the  typical  forms  of  species 
but  no  exact  idea  of  their  limits. 

Statistical  investigation,  as  we  have  already  said,  is 
necessary  to  determine  what  these  limits  are.^  Such  in- 
vestigation teaches  us  not  only  what  the  mean  of  a  char- 
acter is,  but  also  the  range  of  its  variation.  In  the  fore- 
going section  we  have  seen  that  the  deviations  are  often 
so  large  that  neighboring  curves  sometimes  overlap.  This 
is  the  phenomenon  which  I  call  transgrcssive  variabilitw 

Let  us  choose  a  particular  example  to  make  this  phe- 
nomenon clear. 

We  will  select  the  common  species  O.  biennis  L.  and 
O.  ninricata  L.  which,  as  every  one  knows,  can  be  easily 
distinguished  by  the  size  of  their  flowers.  In  the  former 
species  they  are  large  and  project  horizontally  from  the 
stem;  in  the  latter  small  and  erect. 

But  let  us  subject  this  familiar  and  obvious  and  con- 
venient distinction  between  two  species  made  by  Lin- 
naeus himself^  to  statistical  analysis.^    We  measure  the 

^  Beautiful  examples  of  transgressive  curves  are  given  in  a  zoo- 
logical article  of  P.  P.  C.  Hoek^  Nciiere  Lacks-  uiid  Maifischstudicn 
in  Tydschrift  d.  Nederl.  Dierk.  Vereeniging.  (2)  VI,  3,  S.  231-235. 
See  further  G.  Duncker,  On  Variation  in  the  Rostrum  in  Palac- 
monetes  vulgaris.  Americ.  Naturalist,  Vol.  34,  No.  404,  1900  and  of 
the  same  author:  Variation  uiid  Asymtnctrie  bci  Plcuroncctus  iicsiis 
L.,  Wiss.  Meeresunters.  Helgoland,  Bd.  Ill,  Heft  2,  1900. 

^  Spach  in  his  monograph  of  this  genus  also  separates  these  two 
forms  as  species  (O.  vulgaris,  Spach.  =  O.  biennis  L.  :  O.  chrysantho 
Spach.  =^  O.  muricata  L.). 

^The  types  indicated  in  this  book  by  the  names  O.  bioniis  and 
O.  muricata  are  those  found  all  over  Europe,  which  are  probably 
the  prototypes  on  which  Linnaeus  based  his  descriptions.     In  Amcr- 


432       The  Systematic  Value  of  the  New  Species. 

sepals,  the  corolla,  and  the  calyx-tube  for  a  certain  num- 
ber of  flowers;  a  very  great  number  is  not  necessary. 
We  plot  the  measurements  as  in  the  table  on  page  433, 
writing  opposite  each  length  the  number  of  flowers  which 
possess  it.  In  the  case  of  O.  biennis  I  measured  one 
flower  per  plant;  in  O.  muricata  I  did  the  same  (I)  but 
in  the  case  of  a  few  plants  several  per  plant  (II).  All 
the  examples  of  both  species  come  from  the  same  wild 
locality,  a  sandy  spot  near  Zandvoort  (Sept.  1894).  See 
table  p.  433. 

The  measurements^  show  in  the  first  place  that  the 
mean  length  of  calyx  and  corolla  for  O.  muricata  at  that 
locality  is  about  14-15  mm.  and  for  0.  biennis  about 
19-20  mm.  They  confirm  the  alleged  difference  between 
the  two  species.  But  they  show,  further,  that  this  differ- 
ence is  by  no  means  such  that  all  of  the  flowers  of  0. 
biennis  must  necessarily  be  larger  than  those  of  0.  muri- 
cata or  that  in  any  given  case  mere  size  would  settle  the 
question  of  their  specific  identity.  On  the  contrary  the 
largest  flowers  of  O.  miiricata  are  larger  than  the  smallest 
flowers  of  O.  biennis. 

The  mean  differences  are  fixed  and  typical.  But  the 
extreme  variants  overlap — the  ^variability  is  transgres- 
sive. 

But  must  we  conclude  from  this  that  there  is  no 
boundary  between  the  two  species,  that  they  merge  into 
one  another?  Not  at  all.  For  the  flowers  were  picked 
on  undoubted  muricata-  and  biennis--^\2ints>. 

Or  we  may  express  the  case  thus :  the  limits  of  the 

ica  numerous  other  elementary  species  of  both  groups  are  found,  but 
they  have  not  yet  been  described  or  named.     (Note  of  1908.) 

^  I  have  given  above  similar  data  for  the  fruits  of  Oenothera 
leptocarpa  (See  page  357). 


Trans gressive  Variability.  433 


LENGTH  OF 

CALYX 

LENGTH  OF  COROLLA. 

Vlillimeters 

Muricata 

Biennis 

Millimeters 

Muricata 

Biennis 

I 

II 

I 

II 

8 

0 

1 

— 

8 

0 

1 

10 

2 

1 

10 

1 

0 

11 

1 

3 

11 

3 

6 

12 

2 

6 

12 

8 

4 

13 

6 

13 

13 

12 

21 

14 

13 

24 

2 

14 

14 

34 

1 

15 

20 

35 

7 

15 

16 

29 

4 

16 

6 

11 

3 

16 

3 

5 

6 

17 

3 

7 

9 

17 

1 

6 

18 

4 

0 

8 

18 

9 

19 

9 

19 

9 

20 

8 

20 

12 

21 

4 

21 

5 

22 

6 

22 

3 

23 

1 

23 

1 

24 

1 

24 

6 

25 

1 

3     Numb. 

25 

1 

26 

of  flowers 

57 

101 

63 

27 

1 

28 

1 

33 

1 

Flowers,    5;     101  65 

Species  overlap  but  they  will  not  disappear.  And,  con- 
versely, the  homogeneity  of  an  unbroken  series  of  forms 
cannot  be  taken  as  established  until  it  can  be  shown  that 
the  forms  are  grouped  round  a  single  center.  The  exist- 
ence of  two  such  centers  may  point  to  the  existence  of 
two  distinct  types,  even  though  they  seem  to  merge  into 
one  another. 

A  comparison  of  the  length  of  the  calyx  tube  in  the 
two  forms  leads  to  the  same  conclusion.  The  plants  all 
come  from  the  same  locality,  and  the  flowers  were  all 
plucked  from  the  main  stems. 


434       The  Systematic  Value  of  the  Nezu  Species. 

LENGTH  OF  THE  CALYX-TUBE. 

Millimeters         O.  miiricata         O.  bie?inis 


I 

II 

21 

0 

1 

22 

1 

0 

23 

0 

0 

— 

24 

1 

2   • 

25 

3 

6 

26 

6 

8 

27 

8 

11 

28 

8 

15 

29 

12 

15 

30 

10 

17 

31 

4 

15 

1 

32 

3 

7 

2 

33 

1 

1 

2 

34 

0 

1 

2 

35 

1 

1 

0 

36 

0 

1 

1 

37 

0 

38 

3 

39 

3 

40 

4 

41 

3 

42 

3 

43 

1 

Number  of  flowers  58       101  25 

Large  numbers  of  such  tables  could  be  made ;  and  the 
result  would  be  well  worth  the  labor  if  they  demon- 
strated, as  they  most  certainly  would,  that  the  universal- 
ity of  the  law  of  transgressive  variability  is  no  argu- 
ment against  the  independence  and  immutability  of  spe- 
cies. 

Let  us  now  examine  a  second  group  of  characters, 
namely  those  which  do  not  separate  related  species  or  at 
any  rate  only  to  a  very  slight  extent.  In  this  case  the 
mean  values  will  either  coincide  or  show  slight  differ- 
ences caused  by  external  conditions.  For  example  I  found 


Transgressive  Variability.  435 

the  seeds  of  0.  biennis  and  0.  muricata  almost  exactly 
alike  as  to  shape  and  size  in  spite  of  the  considerable 
difference  between  the  seeds  of  a  single  fruit.  The  same 
is  true  of  another  well-known  character,  the  relation  be- 
tween the  length  of  the  corolla  and  that  of  the  filaments. 
I  measured  this  in  ten  flowers  of  0.  muricata  and  in 
twenty  of  O.  biennis  and  found  the  mean  for  the  former 
species  to  be  14.6  and  8.3;  for  the  other  10.0  and  5.5 
mm.,  in  both  therefore  a  proportion  of  100  :  55.  In 
O.  Lainarckiana  however  this  proportion  was  100  :  44. 

The  length  of  the  fruits  is  dependent  to  a  large  extent 
on  the  conditions  of  life.  If  we  examine  plants  which 
have  been  grown  under  diverse  conditions,  we  find  differ- 
ences in  the  lengths  of  the  fruits  and  we  get  series  of 
figures  which  bear  a  superficial  resemblance  to  the  fore- 
going ones  but  are  due  to  different  causes.  See  the  table 
which  follows.  I  measured  the  fruits  in  the  ripe,  prac- 
tically dry  condition,  using  in  each  plant  the  lowest  cap- 
sule on  the  main  stem;  the  plants  were  collected  in  wild 
localities,  but  in  various  places.  The  differences  have  no 
specific  value  and  are  manifestly  due  to  conditions  of 
nutrition.  An  opposite  result  might  have  been  obtained 
under  reversed  conditions. 

Space  does  not  permit  me  to  deal  in  the  same  way  wn'th 
the  variability  of  the  new  species  which  have  arisen  from 
Lainarckiana.  The  great  majority  of  the  characters  are 
without  doubt  transgressively  variable ;  unbroken  series 
could  be  easily  made  with  the  leaves  of  O.  snblincaris  at 
the  one  end  and  those  of  O.  lata  at  the  other;  or  with 
the  fruits  of  O.  oblonga  at  the  one  end  and  those  of 
O.  rubrinervis  at  the  other.  But  whenever  a  sufficient 
number  of  individuals  are  dealt  with,  curves  derived 
from  this  material  are  found  not  to  be  monocentric  but 


436      The  Systematic  Value  of  the  New  Species. 

LENGTHS    OF   THE    FRUITS    OF   THREE    SPECIES    OF    OENOTHERA    IN    MILLI- 
METERS. 

{O.  muricata  1894,  the  rest  in  1893.) 
Millimeters     Larnarckiana      Biennis  Muricata 


15 

1 

16 

1 

— 

17 

5 

18 

11 

1 

19 

17 

4 

20 

27 

9 

21 

Zl 

13 

22 

62 

10 

23 

74 

23 

2 

24 

83 

24 

1 

25 

79 

28 

3 

26 

51 

30 

6 

27 

43 

36 

12 

28 

32 

32 

18 

29 

18 

27 

34 

30 

13 

21 

36 

31 

5 

22 

34 

32 

5 

26 

32 

33 

3 

28 

24 

34 

1 

7 

14 

35 

5 

5 

36 

6 

2 

37 

3 

2 

38 

1 

2 

40 

0 

1 

Number  568  356  228 

polycentric,  each  individual  species  forming  a  perfectly 
definite  group.  The  character  of  each  group  is  given  by 
the  center  of  greatest  frequency,  independently  of  the 
apparent  absence  of  definite  limits. 


Oenothera  Lamarckiana  Seringe. 


437 


§   26.    OENOTHERA   LAMARCKIANA    SERINGE. 

Oenothera  Lamarckiana  belongs  to  the  subgenus  Oma- 
gra which  some  authors  separate  into  a  distinct  genus.  ^ 
Its    most    important    dis- 


tinguishing characters  he  in 
the  seeds  which  are  irregu- 
larly angular  with  ridges 
along  the  angles  and  relatively 
smooth  spaces  in  between 
(Figs.  97  and  98).  These 
characters  make  it  possible  to 
distinguish  them  easily  from 
the  seeds  of  all  other  subdivi- 
sions of  the  genus  Oenothera,'^ 


Fig.  97.  Transverse  section 
through  the  seed  of  Oeno- 
thera Lamarckiana;  cc,  the 
cotyledons  (there  is  no  en- 
dosperm) ;  0,  epidermis;  s, 
areolar  tissue  with  cavities ; 
h,  hard  layer;  ff,  wings  of 
the  seed. 


which  are  either  smooth  ex- 
cept  for  small   indentations,   or  with  a   sort  of  crown 
at  the  upper  end.     The  epidermis  of  the  seed  of  Ona- 

^The  most  important  special  literature  on  this  group  is  the  fol- 
lowing : 

E.  Spach,  Monographia  Onagrearum,  Nouv.  Ann.  Mus.,  IV, 

3,  1835. 
S.  Watson,  Revision  of  the  Extra-tropical  North  American 
Species  of  Oenothera.     Proceed,  Am.  Acad,  of  Arts  and 
Sci.,  Vol.  VIII,  1868-1873. 
Engler  und  Prantl,  Die  natilrl.  Pflanzenfam.,  Ill,  7,  p.   199, 
where  references  to  general  literature  will  be  found. 
The  following  works  must  also  be  mentioned : 

J.  ToRREY  and  Asa  Gray,  Flora  of  North  America,  Vol.   I. 

1 838- 1 840,  p.  492. 
A.  S.  Hitchcock,  Les  Oenotheracees  du  Kansas,  1898. 
H.  Leveille,  Monographic  du  genre  Oenothera   (as  yet  only 
partly  published). 
Onagra  is  given  as  a  subgenus  in  Endlicher,  Genera  Plantanim,  p. 
1 190  sub  No.  61 15;  as  a  genus  in  the  Natilrliche  Pftanzcnfamilicn  of 
Engler  und  Prantl, /.  c.,p.  214;  and  also  in  Britton  and  Brown.  An 
Illustrated  Flora  of  the  Northern    United  States,  Canada  and   the 
British  Possessions,  Vol.  II,  1897,  p.  475. 

^The  various  subgenera  of  Oenothera  are  often  accidentally 
mixed  up  in  botanical  gardens  but  the  above  mentioned  characters  of 
the  seeds  usually  make  it  possible  to  sort  them  out  again  before 
sowing. 


438      The  Systematic  Value  of  the  New  Species, 


gra  which  is  smooth  at  first,  grows  much  faster  than 
the  parts  inside  so  that  it  acquires  wrinkles  and  folds  by 
the  pressure  of  the  surrounding  seeds  (Fig.  98).  As  a 
result  of  this  there  is  great  diversity  in  the  form  of  the 
seeds  of  the  same  loculus.  In  this  respect  the  seeds  of 
the  various  species  of  Onagra  are  practically  all  alike. 

The  fruit  is  an  erect  capsule  which  splits  longitudi- 
nally and  contains  many  seeds.  The  flowers  have  a  long 
calyx-tube,  are  tetram- 
erous  and  apparently 
regular  but  exhibit  as 
a  matter  of  fact,  a 
slight  degree  of  zygo- 
morphy  which  is  most 
pronounced  in  the  fila-  j 
ments.  Prophylls  are 
absent. 

The  species  which 
bore  these  characters 
were  described  and 
named  by  Linnaeus. 
They  were  O.  biennis, 
L.,  O.  miiricata  L.,  and 
O.  parvi flora  L.  To 
these  were  added  later 
the   well-known    forms 

0.  siiaveolcns  Dcsf.  (=0.  grandiflora  Ait.)  and  0.  La- 
marckiana  Ser.  (^0.  grandiflora  Lamarck).^  Besides 
these  there  belong  to  the  group  in  question  a  whole  series 
of  American  forms  which  are  little  known  in  Europe. 

^  Although  the  name  0.  grandiHora  has  -good  claim  to  priorit}' 
for  both  these  species  I  do  not  propose  to  use  it  because  it  has  already 
given  rise  to  a  great  deal  of  confusion.  See  Nederl.  Kriiidk.  Ar chief. 
Aug.  1895. 


Fig.  98.  Seeds.  Lm,  of  O.Lamar  chana, 
seen  from  the  back;  Lm',  seen  from 
the  other  side  which  has  a  sharp 
ridge  on  it;  g,  O.  gigas;  r,  O.  riibri- 
ncrvis;  n,  O.  nanella;  It,  O.  lata;  a, 
O.  alhida;  s,  O.  scintillans,  opened 
and  empty ;  h,  the  hard  layer  which 
surrounds  the  inner  lumen. 


Oenothera  Lamarckiana  Seringe.  439 

Later  systematists  have  either  lumped  all  these  forms 
into  one  big  species  or  have  separated  them  up  in  differ- 
ent ways.  When  they  did  the  former,  they  took  O. 
biennis  as  a  type.  The  other  species  were  ranged  round 
this  as  varieties.  This  was  done  for  example  by  Torrey 
and  Gray  in  their  famous  Flora  of  North  America  and 
by  Watson  in  his  monograph.  This  is  an  important 
point  for  our  further  discussions,  as  showing  that  a 
minute  comparative  study  of  the  various  forms  points 
to  their  common  origin  from  O.  biennis. 

Spach  however  thinks  differently.  He  separates  six 
species  of  Onagra.  Two  of  them  include  all  the  forms 
which  interest  us;  the  rest  are  rare  and  do  not  exist  in 
Europe  either  as  wild  or  as  cultivated  forms.  These  two 
species  are  (1)  Onagra  vulgaris  Spach  =  Oenothera 
biennis  L;  but  also  including  O.  suaveolens  Desf.  and  O. 
Lamarckiana  Ser.  and  (2)  Onagra  chrysantha  Spach, 
which  is  composed  of  O.  muricata  L.,  O.  parz'iflora  L., 
O.  cruciata  Nutt.  and  of  a  Var.  latifolia  with  which  I  am 
not  familiar. 

I  think  it  is  legitimate  to  conclude  from  this  that  the 
original  Oenothera  biennis  has  given  rise  to  the  remain- 
ing species  mairfly  along  three  lines:  1st  by  an  increase 
in  the  size  of  the  flowers  {Lamarckiana),  2d  by  a  de- 
crease in  this  size  {chrysantha)  and  3d  without  any 
change  in  it.  The  other  features  of  the  flowers  are 
closely  correlated  with  its  size  and,  in  fact,  appear  in 
great  measure  to  be  determined  by  it. 

The  species  of  Onagra  differ  from  one  another  not 
only  in  the  structure  of  the  flowers  but  in  that  of  the 
leaves  as  well.  Furthermore  the  fruits  of  0.  parz'iflora 
split  by  8  apical  valves  instead  of  4,  whilst  O.  Lamarck- 
iana has  an  entirely  different  appearance.     Further,  less 


440       The  Systematic  Value  of  the  New  Species. 

important,  distinctions  are  afforded  by  the  degree  of 
hoariness  and  so  forth. 

The  following  questions  suggest  themselves :  Has 
Oenothera  biennis  been  through  a  period  of  mutation 
similar  to  that  through  which  O.  Laniarckiana  is  going 
now?  If  it  has,  did  it  give  rise  to  species  which  now 
exist  in  the  same  way  as  0.  Laniarckiana  is  doing  now? 
Have  the  existing  forms  arisen  directly  from  it  or  do 
they  owe  their  origin  to  repeated  mutations?  Finally 
does  there  exist  anywhere  at  the  present  moment  a  mu- 
table family  of  O.  biennis  which  is  perhaps  giving  off 
some  of  the  forms  which  we  know  and  others,  perhaps, 
as  well  ?  These  and  other  questions  must  for  the  present 
be  set  aside  for  future  investigation  to  answer. 

At  any  rate  they  serve  to  illustrate  the  theme  of  the 
present  chapter,  which  is  that  the  Onagra-group  is  pre- 
cisely parallel  to  the  group  of  mutations  which  is  being 
produced  by  0.  Laniarckiana.  It  is  older  and  perhaps 
more  extensive.  But  if  the  distinctions  between  species 
within  the  two  groups  can  be  shown  to  be  of  the  same 
systematic  value,  the  parallel  between  my  new  species 
and  the  older  species  of  recognized  position  will  strongly 
be  supported  by  pure  systematic  evidence. 

Now  that  I  have  foreshadowed'  the  contents  of  the 
paragraphs  that  follow,  let  us  go  back  to  O.  Laniarckiana.^ 

^  Oenothera  grandiflora  Ait.  =  0.  suaveolens  Desf.  is  often  con- 
fused with  Laniarckiana  either  under  one  of  these  names  or  as  O. 
macrantha  Hort.  The  facts  are  as  follows  It  was  first  described 
by  WiLLDENow  in  his  Species  Plantariim  (Vol.  II,  1799,  p.  306)  but 
seems  to  have  been  figured  before  that  time  by  L'Heritier,  Stirpes 
novae,  Tom.  II,  Plate  4.  De  Candolle  in  his  Prodromiis  suggests 
that  O.  grandiUora  Ait.  and  O.  suaveolens  Desf.  may  perhaps  be  dif- 
ferent species.  Desfontaines  who  gives  no  description  of  it  in  his 
Tableau  (ist  edition  1804,  p.  169;  2d  edition  1815,  p.  195)  seems  to 
regard  the  two  names  as  synonyms. 

In  the  general  Herbarium  of  the  Museum  of  Natural  History  at 
Paris  I  found  in  the  drawer  for  O.  biennis  a  sheet  of  paper  on  which 


Oenothera  Lamarckiana  Seringe.  441 

First  I  shall  give  a  translation  of  Lamarck's  own  de- 
scription of  the  species.  In  order  to  understand  this  we 
must  bear  in  mind  that  Lamarck  was  not  comparing  it 
with  the  forrris  most  closely  related  to  it  but  with  another 
form  with  very  large  flowers,  O.  longiflora,  belonging  to 
another  subgenus.  Moreover  he  had  neither  seen  speci- 
mens from  America,  nor  living  plants  either  wnld  or  culti- 
vated. His  description  rests  on  dried  specimens  in  the 
Paris  Herbarium,  which  had  been  grown  in  the  Jardin 
du  Museum  d'histoire  naturelle. 

Lamarck^s  words  are :  Leaves  entire,  oval-lanceo- 
late, petals  not  indentate,  fruits  glabrous.  This  species 
bears  a  general  resemblance  to  Oenothera  longiflora  but 
can  be  distinguished  from  it  by  a  number  of  obvious 
characters,  in  particular  by  its  branched  stem,  its  entire 
leaves  and  short  and  smooth  fruits.  Its  stem  is  three 
to  four  feet  high,  cylindrical,  almost  glabrous,  of  a  red- 
dish brown  color  with  numerous  projecting  branches. 
The  leaves  are  green,  spirally  arranged,  oval-lanceolate, 
glabrous  on  both  sides  and  entire;  the  lower  leaves  are 
petiolate  and  slightly  toothed  below.    The  bracts  are  nar- 

two  stems  of  Oenothera  grandiHora  Ait.  had  been  stuck.  One  of 
them  bore  this  name  in  the  handwriting  of  Michaux.  At  the  side 
of  the  other  Desfontaines  had  written  Oenothera  snaveolens  Hort. 
Paris.  Somebody  else  had  written  above  it  Oenothera  grandiflora  and 
Poiret  EncycL,  and  there  is  written  underneath  it  in  the  handwriting 
of  Spach  :  Onagra  vulgaris  grandiHora  Spach.,  which  name,  in 
Spach's  Monograph  (p.  353),  is  synonymous  with  O.  grandiflora 
Lam.  Spach  therefore,  we  see,  did  not  distinguish  between  these 
two  grandiHoras  although  they  are  absokitely  unHke  one  another. 

These  two  specimens  are  identical  with  the  form  frequently  cul- 
tivated in  gardens  under  the  name  of  O.  grandiflora  Ait.  z=:  O.  sua- 
veolens  Desf.  I  have  also  often  got  it  under  the  names  of  O.  niae- 
rantha  Hort.  and  O.  odorata  Hort.  (the  latter  name  is  erroneous  and 
is  due  to  the  French  name  Enothere  odorante). 

My  investigations  in  the  Herbarium  at  Paris  have  convinced  me 
of  the" identity  of  the  form  I  cultivate  as  O.  suaz-eolens  Desf.  (O. 
macrantha  Hort.)  with  the  form  described  by  Desfontaines.  Both 
of  them  have  flowers  of  the  same  size  as  those  of  O.  biennis. 


442      The  Systematic  Value  of  the  New  Species. 

rower,  more  pointed  and  sessile.  The  flowers  form  a 
broad  terminal  cluster;  they  arise  singly  from  the  axils 
of  the  bracts  but  are  crowded  close  together.  The  calyx 
is  yellow,  the  tube  somewhat  longer  than  the  four  lan- 
ceolate broad-based  sepals,  which  are  terminated  by  a 
short,  fat,  thread-like  prolongation.  The  four  petals 
are  oval,  very  large,  and  rounded,  almost  as  long  as  the 
calyx-tube  and  tapering  down  to  a  narrow  base.  The 
fruit  is  a  short  capsule ;  it  is  cylindrical,  glabrous,  and 
truncate,  square  in  section  and  is  about  one-third  of  the 
length  of  the  calyx-tube.^ 

The  original  specimens  described  by  Lamarck  are 
still  in  the  Herbarium  of  the  Museum  of  Natural  History 
at  Paris  and  are  marked  there  with  the  same  number  as 
they  are  in  the  Dictionnaire.  I  have  carefully  compared 
these  specimens  with  the  plants  which  I  have  cultivated 
in  my  experimental  garden  and  have  convinced  myself 
of  the  identity  of  the  two.^  The  original  specimens, 
however,  by  no  means  represent  the  mean  type  of  the 
species  in  every  respect  and  therefore  the  description 
does  not  exactly  correspond  to  this  type,  particularly  as 
regards  the  corolla  and  the  fruits.  The  petals  are  ob- 
cordate  but  only  slightly  emarginate  as  compared  with 
O.  longiflora;  the  fruits  are  of  the  same  form  and  size 

"^  Encyclopedic  mcthodique,  Botanique  par  Lamarck,  Tome  IV. 
Paris,  An.  IV  (1796),  pp.  550-554.    Usually  cited  as  Lam.  Diet. 

^  It  appears  that  it  was  not  Lamarck  but  Poiret  who  wrote  the 
section  on  Oenothera  in  the  Dictionnaire.  The  specimens  in  the  Her- 
barium bear  the  note  O.  grandiflora  written  by  Poiret.  In  the  same 
Herbarium  there  is  in  the  case  for  O.  biennis,  a  specimen  of  Oeno- 
thera grandiUora  Lam.  from  the  collection  of  Father  Pourret  :  both 
plants  were  given  to  the  Museum  in  the  year  1847  by  Dr.  Barbier. 
This  plant  was  probably  picked  by  Pourret  in  the  garden  of  the 
Museum  at  the  time  of  his  visit  to  Paris  in  1788.  Later,  Spach 
made  the  following  note  on  this  specimen  :  Onagra  vulgaris  grandi- 
flora Spach,  which  proves  the  identity  of  this  name  with  O.  La- 
marckiana.  This  plant  also  agrees  exactly  with  the  form  I  use  in 
my  cultures. 


Oenothera  Lamarckiana  Seringe.  443 

as  those  of  0.  biennis  and  agree  moreover  with  these  in 
the  amonnt  of  hoariness.^ 

The  subgenus  Onagra,  to  which  O.  Lamarckiana  be- 
longs, comprises  North-American  forms  almost  exclu- 
sively. The  various  forms  growing  wild  in  Europe  have 
been  imported  from  there.  Oenothera  biennis  from  Vir- 
ginia about  1614,  Oenothera  miiricata  from  Canada  in 
1789  by  John  Hunnemann,  Oenothera  siiaveolcns  in 
1778  by  John  Fothergill.^  The  first  two  grow  abun- 
dantly in  the  Netherlands,  on  the  sand  dunes  which 
stretch  along  the  coast,  where  each  consists,  so  far  as  I 
am  aware,  of  a  single  subspecies.  They  are  widely  dis- 
tributed throughout  Europe.  O.  suave olens  grows  wild 
at  the  present  time  in  many  localities  in  the  w^estern  parts 
of  France.^  The  native  country  of  O.  Lamarckiana  is 
unknown,  but  is  probably  Texas. ^  It  only  occurs  wild 
with  us  when  it  escapes  from  gardens. 

One  of  the  characters  of  0.  Lamarckiana  is  the  sym- 
metrical floral  structure,  which  is  best  seen  in  the  sta- 
mens.^ The  flowers  project  sideways  from  the  stem, 
often  almost  horizontally.  The  stamens  are  inclined 
downwards  at  their  base;  the  upper  ones  more  than  the 
low^er  ones;  the  upper  halves  being  more  or  less  erect. 

*I  refer  the  reader  who  is  interested  in  a  further  discussion  of 
the  synonymy  and  wants  a  further  account  of  the  characters  of  these 
species  to  Sur  V Introduction  de  I'Oenothera  Lamarckiana  dans  Ics 
Pays-Bas,  in  Nederlandsch  Kruidkundig  Archief,  Aug.   1895. 

^W.  T.  AiTON,  Hortus  Kcwensis,  2d  edition,  Vol.  II,  1810,  p.  34i- 

^GiLLOT,  Sac.  Bot.  France,  1893,  p.  197.  See  also  Tome  III,  p.  437- 

*The  strain  which  is  now  being  cultivated  in  European  gardens 

was  introduced  from  Texas  about   i860.     See  Bcr.  d.  dcutsch.  Bot. 

Gesellschaft,  1905,  Bd.  XXIII,  p.  382.     (Note  of  1908). 

^H  VocHTiNG,  Ueher  Zygomorphie  und  deren  Ursachcn,  in 
Pringsh.  Jahrb.  f.  wiss.  Bot,  Vol.  XVII,  1886,  p.  311.  See  Plate 
XVI,  Fig.  14,  in  particular.  For  an  account  of  geotropical  curvations 
of  Ocnothera-^owtrs,  see  also  Hanstein,  Beitrdgc  cur  allg.  Morpho- 
logic,  IV,  3,  p.  151- 


444      The  Systematic  Value  of  the  New  Species. 

VoCHTiNG  found  that  this  symmetrical  bending  was  due 
to  gravity.  He  fixed  branches  to  a  chnostat  and  observed 
that  the  flowers  opened  normally  but  that  the  filaments 
remained  straight.  Neither  light  nor  darkness  had  any 
influence  on  these  processes.  The  bending  of  the  fila- 
ments takes  place  just  before,  or  during  the  unfolding 
of  the  flower.  If,  about  the  middle  of  the  day  on  the 
evening  of  which  the  flower  will  open,  we  open  a  bud 
we  find  the  filaments  perfectly  straight.^ 

It  follows  from  this  that  the  degree  of  bending  in 
the  filament  depends  on  the  angle  which  the  open  flower 
makes  with  the  perpendicular.  The  smaller  the  angle 
the  less  the  bend. 

In  all  these  respects  our  species  behaves  like  O.  bien- 
nis. On  the  other  hand  in  O.  miiricata  and  O.  parviflora 
the  filaments  are  not  bent.^  The  absence  of  bending  in 
this  case,  however,  directly  depends  on  the  fact  that  the 
flowers  in  these  species  instead  of  projecting  sideways 
stand  up  erect.  As  a  matter  of  fact,  this  bending  is  not 
entirely  absent;  I  always  found  some  signs  of  it  even  if 
they  were  only  very  slight  ones. 

§   27.     SYNOPSIS   OF   THE   CHARACTERS    OF   THE   NEW 

SPECIES. 

My  new  species,  without  exception,  possess  the  gen- 
eral characters  of  the  biennis-gvon^  to  which  0.  La- 
in arckiana  belongs.  According  to  Watson^s  Monograph 
of  the  genus,  the  following  are  the  characters  of  this 
group.  •^' 

^  See  the  Figure  on  page  218. 

^  Bull.  Soc.  Bot  France,  T.  Ill,  p.  437. 

^  Sereno  Watson,  Revision  of  the  Extra-tropical  North  Amer- 
tcan  Species  of  the  Genus  Oenothera,  Proc.  Amer.  Acad,  of  Arts 
and  Sciences,  May,  13,  1873,  Vol.  VIII,  pp.  573-618. 


Characters  of  the  New  Species.  445 

Plants  annual  or  biennial,  forming  an  erect,  for  the 
most  part  branched  stem.  Flowers  yellow,  buds  erect, 
surmounted  by  the  four  tips  of  the  calyx.  Anthers  lin- 
ear, each  inserted  at  its  center  upon  filaments  of  equal 
length.  Stigma  formed  of  four  or  more  long  cylindrical 
parts,  which  are  either  free  or  more  or  less  fused  later- 
ally. Calyx  tube  narrow,  slightly  broader  at  the  top. 
Fruits  sessile,  oblong,  tapering  upwards;  seeds  in  two 
rows  in  each  loculus ;  the  integument  of  the  seeds  too 
big  for  the  kernel  and  therefore  wrinkled. 

This  list,  taken  in  conjunction  with  the  following 
tables,  will  suffice  to  show  that  the  new  species  belong 
to  the  group  in  question  both  morphologically  and  sys- 
tematically. That  they  are  more  closely  related  to  O. 
Lamarckiana  than  to  0.  biennis,  O,  niuricata,  0.  sua- 
veolens  or  the  other  species  of  this  group  described  in 
systematic  works,  is  shown,  apart  from  their  origin,  by 
certain  characters  of  the  flowers.  In  the  first  place  these 
are  much  larger  than  they  are  in  the  other  forms ;  and, 
in  the  second,  they  have  a  longer  style.  The  style  raises 
the  stigma  in  the  bud  above  the  tips  of  the  anthers.  When 
the  flower  opens  the  four  stigmas  expand  into  the  form 
of  a  cross,  not  touching  the  anthers,  however,  as  a  rule. 
In  0.  biennis  on  the  other  hand  the  stigmas  lie,  in  the 
bud,  between  the  anthers  and  do  not  reach  above  them  at 
the  time  of  flowering. 

This  state  of  affairs  is  very  important  from  the  point 
of  view  of  fertilization.  In  O.  biennis  this  takes  place  in 
the  bud  because  the  anthers  dehisce  a  whole  day  before 
the  flower  opens;  though  the  exact  time  of  this  is  of 
course  subject  to  some  variation.  This  fact  obviously 
makes  the  operation  of  castration  preliminary  to  crossing 
much  more  difficult,  because  it  has  to  be  done  on  very 


446       The  Systematic  Value  of  the  New  Species. 

young  buds.  On  the  other  hand  it  faciHtates  self-fertili- 
zation by  rendering  it  superfluous  to  do  more  than  exclude 
the  visits  of  insects.  A  very  different  state  of  things 
obtains  in  Oen.  Lamarckiana.  Here  castration  can  be 
easily  and  safely  effected  even  in  large  buds ;  but  in  self- 
fertilization  the  pollen  has  to  be  actually  transferred.  In 
this  respect  all  the  new  species  except  0.  lata  and  O. 


Fig-  99-    Ripe  fruits  shortly  before  drying,  half  natural  size. 
L,  Oenothera  Lamarckiana;  R,  O.  rubrinervis ;  A,  O.  albida. 

hrevistylis  and  the  sterile  forms  behave  exactly  like  0. 
Lamarckiana  and  not  like  O.  biennis.  The  necessity  of 
fertilizing,  year  after  year,  with  my  own  hand  every 
single  flower  from  which  I  wanted  to  save  seed  has 
given  me  sufficient  experience  on  this  point. 

In  the  description  of  the  species  (§§  10-23)  I  made 
occasional   reference  to  atavistic  phenomena.     For  ex- 


Characters  of  the  New  Species. 


447 


ample  0.  nanella  in  its  earliest  stages  forms  a  few  long- 
stalked  leaves;  and  occasional  crumples  are  seen  in  the 
otherwise  smooth  leaves  of  O.  laevifolia  and  0.  scintil- 
lans,  etc.  In  this  they  behave  like  many  species  even  in 
other  families  which  reproduce  in  their  early  stages  the 
characters  of  their  ancestors  (for  example  Acacia,  Ulcx, 
Stum,  etc.). 

I  shall  now  attempt  to  set  forth  the  characters  of  the 


Fig.  100.  Ripe  fruits  shortly  be-  Fig.  loi.  Ripe  fruits,  shortly  be- 
fore drying;  half  nat.  size;  the  fore  drying,  half  natural  size, 
bracts  have  not  yet  fallen  off.  o,  G,  Oenothera  gigas;  Lt,  O.  lata. 
O.  oblonga;  s,  O.  scintillans. 

new  species  in  synoptic  tables  in  order  to  make  it  easier 
to  compare  them  with  the  characters  of  the  older  species 
in  the  section  which  follows.  And  in  order  to  express 
myself  as  simply  as  possible  I  shall  regard  the  character 
of  the  parent-species  O.  Lamarckiana  as  the  normal  and 
compare  the  others  with  it. 

Further  I  propose  to  deal  with  the  different  organs 


448       The  Systematic  Value  of  the  New  Species. 

and  developmental  stages  separately  in  the  tables;  and  I 
shall  start  with  the  seedlings  at  the  age  (2-3  months)  at 
which  they  are  usually  sorted  out  and  recorded.  The  first 
table  therefore  gives  the  characters  which  are  used  in  this 
sorting. 

ANALYTICAL  TABLE  OF  SEEDLINGS. 
I.  Leaves  stalked. 

A.  Leaves  of  the  same  breadth  or  broader.^ 

1.  Of  the  same  breadth  and  shape,  not 
to  be  distinguished  as  seedlings. 

a)  (Fig.  48,  51,  52,  64,  65,  66,  72,  95)     1.  O.  Lamarckiana. 

b) 2.  O.  bj-cvistylis. 

c)       3.  (9.  leptocarpa, 

2.  Broader,  pointed,  with  many  crum- 
ples. 

(Fig.  52,  63,  65,  66) \.O.gigas. 

3.  Broader,  rounded  at  the  tip  with  very- 
deep  crumples,  edge  incurved. 

a)  (Figs.  48,  51,  52,  91,  9^,  95)       .     5.  O.  lata. 

b) 6.  6^.  semilata. 

B=  Leaves  narrower. 

1.  Broadest  in  the  middle. 

a)  very  long  with  long  stalks,  with 
narrow     veins,     almost     smooth 

(Fig.  83) 1 .  O.  elliptica. 

b)  small  with  broad  leaf-stalk  and 
broad  principal  veins,  very 
smooth,  shiny,  dark  green  (Figs. 

51,81,82) S.  0.sci7ihllans. 

2.  Of  equal  breadth  over  the   greater 
part  of  their  length. 

a)  green. 

a)  1.  Only  slightly  narrower, 
smooth  without,  or  al- 
most without,  crumples  .     9.  O.  laevifolia. 

a)  2.  Very  narrow  with  broad 
leaf -stalks  and  broad 
veins  which  often  are 
reddish;  wrinkled  (Figs. 
48,  53,  72,  73,  74,  95)  .     .  10.  O.  oblonga. 

*"(than  in  Lamarckiana)"  as  also  in  the  other  analytical  tables. 


Characters  of  the  New  Species.  449 

b)  whitish, 

b)   1.  Crumples  many,  pointed, 

narrowing    ofif    into    the 

stalk  (Figs.  48,  72,  75,  76, 

95) 11.  O.albida. 

b)  2.  Crumples  few,  narrowing 

off  into  the  stalk,  wavy, 

brittle,    veins    reddish — 

(Figs.  52,  68)       ....  12.  O.  rubrinervis. 
b)  3.  Crumples    few,    scarcely 

narrowing    off    into    the 

stalk,  almost  grasslike    .  13.  O.  sublinearis. 

II.  Leaves  sessile,   short    and    broad,    almost 

heartshaped,  crumpled  (Figs.  51,  52,  78,  79)  14.  O.  nanelLa. 

The  new  species  can  best  be  distinguished  from  one 
another  by  their  so-called  habit.  This  is,  as  in  the  case 
of  O.  Lamarckiana  itself,  largely  dependent  on  external 
conditions.  In  the  first  place  biennial  plants  are  as  a  rule 
naturally  stronger  than  annual  ones.  The  former  are 
sometimes  more  than  two  meters  high;  the  latter  often 
little  more  than  a  meter.  In  both  cases  the  time  of  sow- 
ing makes  a  difference;  the  earlier  the  plants  come  up 
the  more  time  they  have  for  their  full  development.  The 
height  and  amount  of  branching  of  the  plants  are  largely 
dependent  upon  the  amount  of  sunshine  they  get,  and  on 
whether  they  are  growing  close  together  or  not. 

The  result  of  this  is  that  spurious  differences,  which 
are  either  indirectlv  connected,  or  not  connected  at  all, 
with  real  specific  characters,  may  appear  in  comparing  cul- 
tures of  related  species,  and  obscure  the  real  differences. 
On  the  other  hand  genuine  differences  sometimes  tend 
to  become  obliterated.  But  if  uniformity  of  treatment  is 
insured,  beds  of  my  new  species  have  a  perfectly  distinct 
and  different  aspect  and  can  be  recognized  with  certainty, 
even  at  a  distance. 


450       The  Systematic  Value  of  the  New  Species. 

The  following  table  mainly  refers  to  annual  plants 
in  flower. 

ANALYTICAL  TABLE  OF  FLOWERING  PLANTS:   HEIGHT  AND 

MODE  OF  BRANCHING 

I.  Of  the  same  or  nearly  the  same  height  (1  5 — 
1.8  m). 

A.  Flowering  over  in  October.     Stem  erect, 
rigid 

1.  Of  the  same  strength. 

a)  Secondary  stems  strong,  branches 

short,  foliage  lax  (Fig.  55)  ...  1.  O.  Lamar ckiana. 

b)  Secondary  stems  weak,  main 
stem  branched;  infrutescence  lax; 
stem  reddish,  brittle,  often  wavy 

(Fig.  49,  67,  69,  70) 2.  O .  rubrinervis . 

2.  A  little  weaker. 

a)  Leaves  narrow,  very  much  like 

O.Z«w.  (Fig.  56) 3.  O.laevifolia. 

b)  Leaves  broad,    like   O.  lata  but 

taller 4.  O.semilata. 

3.  Very  strong,  stem  stout  and  very 
erect,  dense  foliage,  short  internodes, 
branches  short  and  rosette-like.  In- 
florescence closer  and  fuller     ...  5.  O.gigas. 

B.    Flowering  continues  till  winter.    Weak 
and  drooping  at  that  time. 

1.  Much  branched;  flowers  many;  group 

of  buds  above  the  flowers  small  .     .  6.  O.btevistylis. 

2,  Slightly  branched;  flowers  rare; 
group  of    buds    above    the    flowers 

very  long 7.  O.leptocarpa. 

IL  Shorter  (about  a  meter  or  less). 
A.  Much  branched. 

1.  Branches  pressed  close  to  stem;   the 
whole  plant  rigid.    Bud-bearing  zone 

above  the  flowers  long 8.  C?.  scintillans. 

2.  Branches  projecting  outwards,  rigid. 

a)  Main  stem  thick,  projecting  above 

the  branches 9.  O.albida. 

b)  Short,  weak 10.  (9.  elliptica. 

c)  Usually  very  weak W.  O.  sublinearis. 


Characters  of  the  New  Species.  451 

3.  Branches  weak,  and  so  bent  down- 
wards, top  of  plant  also  weak  .     .     .12.  O.  lata. 
B.    Almost  unbranched,    branches   in  the 
form  of  rosettes,  stem  very  thin  (Fig. 

50,  71).     .     . U.  O.oblonga. 

III.    Dwarf,  often   flowering  when   only   10-20 

cm.  high  (Fig.  45,  77) 14.  O.nanella. 

In  Oenothera  Lamarckiana  every  part  of  the  plant  has 
a  characteristic  type  of  leaf  from  the  seedling  to  the 
top  of  the  inflorescence.  The  same  is  true  of  the  new 
species  which  have  arisen  from  it.  The  radical  leaves 
of  the  full  grown  rosettes  merge  by  imperceptible  de- 
grees into  the  lower  leaves  of  the  stalk.  As  we  ascend 
the  stem,  the  leaves  become  gradually  shorter  and  set 
on  smaller  stalks  until  we  reach  the  inflorescence,  at  the 
bottom  of  which,  or  slightly  later,  they  become  almost 
sessile.  In  the  young  inflorescence  they  extend  beyond 
the  flowers,  but,  later  on,  become  relatively  small  com- 
pared with  them.  The  greatest  breadth  of  the  leaf, 
which  at  the  bottom  of  the  plant  is  about  its  middle, 
gradually  shifts,  as  we  ascend,  to  its  base.  In  describing 
the  leaves  of  the  different  new  species  we  must  therefore 
compare  only  such  as  are  borne  on  the  same  part  of  the 
stem. 

ANALYTICAL  TABLE  OP  THE  LEAVES. 
I.  Of  normal  breadth. 

A.  Of  normal  length  and  form. 

1.  Pointed. 

a)  (Figs.  62,  89) \.  O.  Lamarckiajia. 

b) 2.  O.  leptocarpa. 

2.  Rounded 3.  O.  brevisfylis. 

B.  Roundish 4.  (7.  semilata. 

C.  Short,  sessile  or  with  a  short  stalk;  broad  at 

the  base;  often  auriculate  or  heart  shaped  5.  O.  nanella. 
II.  Broader. 

A.  Of  the  same  form,    but  very  variable, 
teeth  large,  numerous,  especially  at  the 


452      The  Systematic  Value  of  the  New  Species. 

base.     Those  on  the  stem   bent  down- 
wards.    (Fig.  54,  62) 6.  O.gigas. 

B.  Round,  stumpy,  slightly  toothed,  but 
usually  with  an  incurved  edge  (Fig.  57, 
58,  88,  89) 1.  O.  lata. 

III.  A  little  narrower. 

A.  Green. 

1.  Smooth,  without  crumples. 

a)  Of  normal  length,  flat 8.  (9.  laevi folia. 

b)  Small,  median  vein  broad,  whitish 

(Fig.  54) .     .     .     9.  6>.  sci7itillans. 

2.  Uneven;  radical  leaves  narrow  with  a 
broad  vein;  leaves  on  the  stem  sessile 

and  with  a  broad  base  (Fig.  54)    .     .   10.  O.  oblonga. 

B.  Whitish. 

1.  Often  with  red  veins;  broadest  in  the 
middle,   bracts  folded  longitudinally 

(Fig.  54) 11.  (9.  riibrinervis . 

2.  Sessile  with  a  narrow  base;  only  the 

lower  leaves  stalked  (Figs.  54,  57)     .  12.  O.  albida. 

IV.  Very  narrow. 

A.  Lanceolate,  long,  often  ten  times  as  long 

as  broad  (Fig.  83) 13.  6>.  elliptica. 

B.  Almost  linear,  small  (Fig.  85,  86)       .     .  14.  O .  subh7iearis . 

To  turn  now  to  the  flowers ;  I  have  already  stated 
above  that  their  size  depends  largely  on  the  strength  of 
the  plant  which  bears  them.  They  exhibit  both  indi- 
vidual and  partial  variability  and  follow  Quetelet's 
law  in  these  respects.  A  very  striking  fact  is  that  their 
size  gradually  diminishes  during  the  flowering  period 
(which  lasts  from  July  till  October)  and  that  at  the  end 
of  it  they  sometimes  sink  to  %  or  even  half  their  orig- 
inal size.  This  is  obviously  determined  by  the  exhaustion 
of  the  plant  by  fructification ;  for  O.  hrevistylis,  which 
sets  practically  no  seed  and  often  goes  on  flowering 
until  well  into  November,  bears  large  and  bright  flowers 
even  at  that  time.  The  flowers  are  smaller  on  the  lat- 
eral branches  if  the  main  stem  is  laden  with  fruits.     But 


Characters  of  the  New  Species. 


453 


if  part,  or  all  of  this,  has  been  cut  off  during  early  life 
(as  is  often  done  for  the  purpose  of  artificial  fertiliza- 
tion) the  lateral  branches  bear  remarkably  large  and  fine 
flowers. 

It  follows  from  this  that  those  new  species  which  are 
of  a  delicate  nature  will  have  somewhat  smaller  flowers. 

ANALYTICAL  TABLE  OF  FLOWERS,   FRUITS  AND  SEEDS. 

(Figs.  98-101.) 

I.  Flowers  as  large  or  larger,  petals,  on  the 
average  3-4  cm.  long  (plants  large). 

A.  Fruits  and  seeds  normal;  buds  thin;  ta- 

pering to  the  top  (Fig.  99). 

1.  Calyx  and  fruits    green,   sometimes 

slightly  reddish  (Fig.  61)       .     .     .     .     1    O.  Laniarckiana 

2.  Calyx  reddish,  fruits  striped  with  red, 
petals  often  more  or  less  crumpled, 

broad,  becoming  darker  as  they  fade     2.  O  rubrinervis. 

3.  Pale  yellow;    the  later  flowers  with 

oval  petals  (Figs.  59,  60)        .     .     .     .     3.  O  laevifolia. 

B.  Fruits  short  and  thick  (Fig.  101). 

1.  Seeds  dark  brown,  large  and  plenti- 
ful; petals  very  broad;  buds  thick     .     4    Ogigas. 

2.  Seeds  large,  scanty;  buds  fat;  petals 
crumpled;  anthers  sterile  (Fig.  46)    .     5.  O  lata. 

3.  Almost  the  same,  pollen  fertile     .     .     6.  6>  semilata. 

C.  Fruits   short  and  thin,    flowers    short- 

styled,  ovary  partly  superior     .     .     .     1 .  O.  brevistylis. 

D.  Fruits  long  and  thin.     Flowering  does 

not  begin  until  late  in  the  summer 
and  lasts  well  into  the  autumn      .     .     8.  O.  leptocarpa. 
IL  Flowers  smaller,  or  very  nearly  as  large; 
petals  about  3  cm.  long  (plants  short). 

A.  Fruits  long  and  thin;  flowers  much  ex- 

panded; petals  elliptical. 

a)  Fig.  84 ^    O.  elHpUca. 

b)  Fig.  87 10.  (7.  sublinearis 

B.  Fruits  of  almost  normal  size. 

a)  Seeds  plentiful,  of  almost  nor- 
mal size.  Buds  often  laterally 
twisted \\.  O.  nayiella. 


454       The  Systematic  Value  of  the  New  Species. 

b)  Fruits  thinner,  poor  in  seed;  flowers 
pale  yellow,  corolla  less  expanded. 

(Fig.  88,  89) 12.  O.  albida. 

C.  Fruits  short  and  thick,  of  half  the  normal 
size  or  less. 

a)  Flowers  erect;    seeds  small;    fruits 

smooth 13.  (9.  scintillans 

b)  Flowers  projecting  sideways;  fruits 

not  so  stout,  poor  in  seed      .     .     .   14    O.  oblonga. 

The  characters  given  in  these  tables  are  those  which 
I  have  myself  ordinarily  employed  in  sorting  and  record- 
ing my  plants.  But  there  are  also  small  differences 
which  practice  enables  one  to  recognize  with  ease,  and  to 
emplo}^  with  certainty.  It  is,  however,  almost  impossible 
to  express  them  in  words.  And  the  above  mentioned 
circumstance  that  the  degree  of  development  of  all  the 
organs  is  highly  correlated  with  the  individual  strength 
of  the  plant  always  makes  descriptions  appear  incom- 
plete ;  but,  on  the  other  hand,  materially  facilitates  the 
discriminations  of  the  living  material. 

§  28.    COMPARISON  OF  THE  CHARACTERS  OF  THE  OLD 

AND  NEW  SPECIES. 

The  new  species  which  have  arisen  in  my  experi- 
mental garden  from  Oenothera  Laiuarckiana  differ  from 
one  another  in  the  same  way  as  do  the  already  known 
species  of  the  bieiinis-group.  I  shall  now  endeavor  to 
prove  this  important  generalization  by  a  detailed  com- 
parison of  the  two  groups.  Unfortunately  the  difficulty 
of  giving  this  proof  is  considerably  enhanced  by  the  in- 
completeness of  the  descriptions  which  have  been  given 
in  the  literature.  The  diagnoses  are  usually  short,  often 
based  on  single  herbarium  specimens  about  which  we 
have  no  means  of  knowing  in  what  characters  they  repre- 


Comparison  of  the  Old  and  New  Species.        455 

sent  the  mean  of  the  type  and  in  what  they  deviate  from 
it,  and  if  so,  to  what  extent.  There  is  practically  no  in- 
formation about  the  seedlings ;  and  this  would  have  been 
particularly  valuable  in  this  case.     And  so  forth. 

These  gaps  in  the  literature  can  of  course  best  be 
filled  up  by  growing  the  species  in  question :  and  for 
many  years  I  have  cultivated  the  forms  which  grow 
wild  with  us  and  some  other  ones,  on  a  large  scale  and 
under  different  conditions.  In  1895  I  procured  in  ex- 
change from  the  botanical  gardens  all  the  available  sam- 
ples of  seed  of  the  subgenus  Onagra  and  sowed  as  many 
of  these  as  I  could  manage.  And  since  then  I  have  taken 
every  opportunity  that  offered,  of  procuring  Onagra- 
seeds. 

I  am,  of  course,  most  familiar  with  the  forms  which 
grow  wild  with  us,  0.  miiricata  and  O.  biennis;  but  I 
only  possess  one  form  of  each  of  these. ^  I  am  familiar 
with  0.  suavcolens  which  is  widely  distributed  over 
France  and  have  two  subspecies  of  it;  with  0.  hirsutis- 
sinia  (O.  biennis  hirsutissima  Torrey  and  Gray)  ;  with 
0.  parz'iflora  L.  and  0.  cntciata  A'utt. ;  and  with  some 
others.  I  am  only  acquainted  with  figures  or  herbarium 
specimens  of  O.  spectabilis  Spach  (0.  corynibosa),  O. 
elata  Kunth,  0.  media  Link,  0.  erosa  Lchni.,  etc.  But 
they  are  intermediate  in  character,  so  far  as  it  is  pos- 
sible to  judge,  between  the  two  species  mentioned  first ; 
in  fact  they  bridge  over  the  gap  between  these  two  to 
a  large  extent. 

For  these  reasons  I  shall  confine  myself  almost  en- 
tirely to  the  comparison  of  the  new  species  with  0. 
biennis,  O.  miiricata,  0.  Lamarckiana,  O.  crnciafa  and 

*  Probably  the  types,  used  by  Linnaeus  for  bis  descriptions. 
Compare  Note  on  page  431.     (1908.) 


4S6      The  Systematic  Value  of  the  New  Species. 

O.  suavcolcns.  This  will  be  sufficient  to  show  that  the 
differences  between  the  former  are  greater  than  those 
between  the  latter.  A  study  of  the  other  old  species 
would  obviously  only  serve  to  bear  out  this  conclusion. 

Let  us  begin  with  the  seedlings.  They  fall  into  two 
groups.  O.  biennis  and  O.  Lamarckiana  have  broad 
leaves  (Fig.  102  A),  O.  muricata,  0.  cruciata  and  0. 
suave olens  narrow  ones   (Fig.  102  B). 

These  differences  can  be  seen  particularly  well  in 
very  young  rosettes ;  but  when  the  leaves  begin  to  grow 
quickly  as  they  do  in  June  they  all  become  longer  and  their 
distinguishing  feature,  therefore,  less  striking  (Fig.  103), 


Fig.  102.     Seedlings.    A,  of  Oenothera  biennis  L. ;  B,  of 
O.  muricata  L.,  two  months  old. 

only  however  to  become  quite  clear  again  later  on.  I 
have  often  grown  rosettes  of  various  new  and  old  spe- 
cies in  rows,  close  to  one  another,  in  order  to  compare 
10-20  or  more  individuals  of  the  same  age  and  under  the 
same  conditions.  O  muricata  and  0.  scintillans  differ 
most  widely  from  the  normal  in  the  narrowness  of  their 
leaves ;  in  both  of  them  the  leaves  are  smooth  and  shiny ; 
in  the  former  however  they  are  pale  green  and  long,  in 
the  latter  dark  green  and  short.  O.  ruhrinervis,  O. 
suaveolens  and  O.  hirsutissima  have  wavy  crumples  and 


Comparison  of  the  Old  and  New  Species.        457 

pale  leaves.  They  look  very  much  alike  when  young, 
but  the  first  of  them  can  be  distinguished  earlier  and  with 
greater  certainty  from  its  neighbors  (in  hybrid  crops 
for  example).  Rosettes  of  0.  gigas  are  much  larger  and 
stronger  than  those  of  O.  Lamarckiana ;  these  are  about 
as  vigorous  as  O.  biennis,  but  their  leaves  are  not  smooth 
like  those  of  O.  hiennis  but  uneven.  O.  elliptica  is  often 
scarcely  distinguishable  from  O.  cruciata;  0.  suhlinearis 


Fig.  103.  Full  grown  leaves  of  young  rosettes  in  June  at 
the  age  of  3  months.  B,  O.  biennis;  M,  O.  muricata;  S, 
O.  suaveolcns. 

has  the  narrowest  leaves  of  the  whole  group.  Between 
this  latter  and  0.  gigas  the  various  old  and  new  species 
form  a  perfect  series  of  transitional  forms. 

Although  single  individuals  or  their  figures  convey 
only  a  very  imperfect  impression  of  a  species,  I  invite 
the  reader  to  compare  Figs.  102  and  103  with  those, 
which  have  already  been  given,  of  rosettes  and  leaves. 


458       The  Systematic  Value  of  the  Nezv  Species. 


First  with  the  groups  of  leaves  from  rosettes  in  June 
(Fig.  52,  p.  293  and  Fig.  53,  p.  294)  ;  and  then  with  the 
rosettes  of  O.  gigas  (Fig.  63,  p.  324),  O.  lata  (Fig.  92, 
p.  412);  O.  scintillans  (Fig.  82,  p.  383),  O.  oblonga 
(Fig.  74,  p.  344)  and  so  forth. 

The  radical  leaves  of  the  full  grown  rosettes  and  the 
leaves  on  the  stem  behave  in  the  same  way.  Those  of 
O.  biennis  and  0.  Lamarckiana  hardlv  differ  at  all  in 


Fig.  104.  Radical  leaves  of  full  grown  rosettes.  B,  of 
OenotJiera  biennis;  L,  of  O.  Lamarckiana.  The  spots  on 
the  leaves  are  brown  in  life. 

form  (Fig.  104  B  and  L).  Those  of  the  former  are 
smooth  with  few  crumples,  with  red  main  nerves,  and 
often  a  number  of  scattered  brown  spots;  the  latter  are 
very  much  wrinkled,  without  red  pigment  or  at  most 
with  no  more  than  isolated  red  spots.  In  form.  0.  gigas 
differs  somewhat  more  (Fig.  62  on  page  323)  and  0. 
lata  more  still  (Fig.  58,  p.  311,  and  Fig.  89,  p.  405). 


Comparison  of  the  Old  and  New  Species.        459 

At  Fig.  105,  p.  460  will  be  seen  a  group  of  stem 
leaves  for  comparison  with  the  corresponding  ones  in 
Fig.  54  on  page  295.  The  differences  are  obviously  of 
the  same  order.  In  the  case  of  O.  cruciata  and  0.  nniri- 
cata  (Fig.  105,  p  and  in)  they  are  most  pronounced; 
and  still  more  so  in  O.  elliptica  and  O.  sublinearis,  which 
are  not  included  in  Fig.  54. 

With  regard  to  ''habit"  the  majority  of  the  older 
species  do  not  differ  much  from  one  another.  0.  nniri- 
cata  has  usually  stronger  lateral  branches  than  0.  biennis; 
O.  Lamar ckiana  has  a  longer  spike  than  either.  0.  cru- 
ciata is  shorter  than  O.  biennis,  which,  however,  0. 
siiaveolens  and  O.  hirsutissima  very  much  resemble, 
though  they  are  less  robust.  All  these  comparisons  are 
of  course  made  between  plants  under  similar  conditions 
of  cultivation.  Under  such  conditions  O.  rubrinervis,  0. 
gig  as,  O.  laevi folia  and  0.  brevistylis  do  not  differ  so 
much  from  Lamar  ckiana  as  do  the  shorter  forms  which 
have  an  entirely  different  habit.  Amongst  these  O.  lata 
is  broad,  close  and  compact  whilst  O.  oblonga  and  0. 
scintillans  with  their  narrow  leaves  have  a  rigid  and 
thin  stem  which  branches  only  slightly  or  not  at  all. 

The  glaucous  color  of  O.  mtiricata  is  characteristic 
of  this  species;  the  green  of  0.  albida  is  paler  than,  and 
that  of  0.  rubrinerms  about  the  same  as  that  of  O.  siia- 
veolens and  O.  hirsutissima.  These  four  forms  are  very 
much  alike,  apart  from  their  flowers  and  fruits. 

With  regard  to  the  flowers  the  differences  are  much 
greater  between  the  older  species  than  they  are  between 
the  new  ones.  The  flowers  are  small  in  O.  miiricata, 
0.  parviflora  and  0.  cruciata:  medium  in  O.  bienjiis,  O. 
snaveolens  and  O.  hirsutissima,  and  very  large  in  O. 
Lamarckiana.    In  the  first  group  they  are  erect,  and  their 


460       The  Systematic  Value  of  the  New  Species. 

stamens  therefore  not  bent  (see.  p.  444)  ;  in  the  two  latter 
groups  they  project  outwards  and  the  androecium  is  mod- 
ified correspondingly.     In  Lamarckiana  the  stigma  ex- 


Fig.  105.  Stem-leaves  of  Oenothera  biennis  (b)  ;  O.  sua- 
veolens  (s)  ;  O.  hirsutissima  (h)  ;  O.  cniciata  (p)  ;  O. 
muricata  (m)  ;  to  be  compared  with  Fig   54  on  p.  295. 

tends  beyond  the  anthers ;  it  reaches  the  same  level  in  the 
other  forms. 


Comparison  of  the  Old  and  New  Species.        461 

In  all  these  and  other  details  the  new  species  have  the 
flowers  of  Lamarckiana.  But  during  the  last  two  years 
my  mutants  have  overstepped  even  this  limit;  one  hav- 
ing appeared  with  hicnnis-^ow^vs  and  one  with  ;//z/n'ca/a- 
flowers,  not  however  in  pure  but  in  crossed  strains. 

A  curious  form  must  be  mentioned  here,  Oenothera 
cruciata  Nuttall  which  is  described  by  some  systematists 
as  a  species,  but  regarded  by  others  as  a  variety  of  O. 
parviflora,  from  which  it  differs  by  its  small  linear  petals 
but  in  no  other  respect.  It  is  therefore  more  closely  allied 
to  O.  parviflora  than  any  two  of  my  new  species  are  to 
one  another. 

Lastly  let  us  look  at  the  fruits.  The  older  species 
resemble  each  other  with  the  exception  of  O.  parviflora, 
in  which  the  capsule  is  described  as  opening  by  eight 
valves  instead  of  four.  The  other  alleged  differences 
such  as  cylindrical  or  conical  form,  greater  or  less  degree 
of  hoariness,  length  and  thickness,  etc.  are  subject  to  a 
very  great  extent  to  individual  fluctuations  and  do  not 
seem  to  constitute  differences  of  specific  rank. 

On  the  other  hand  it  is  just  in  the  characters  of  the 
fruits  and  seeds  that  the  new  species  differ  most  amongst 
one  another,  as  the  table  on  page  453  and  Figures  98 
(group  of  seeds,  p.  438)  and  99-101  (fruits,  pp.  446- 
447)  clearly  show. 

We  can  sum  up  by  saying  that  the  known  systematic 
species  of  the  subgenus  Onagra  differ  from  one  another 
in  essentially  the  same  way  as  do  the  forms  which  have 
arisen  from  0.  Lamarckiana.  The  two  groups  are  pre- 
cisely analogous.  The  relation  between  the  group  of 
Owflf^ra-species  and  O.  biennis  is  the  same  as  that  between 
the  group  of  Lamarckiana-mwtdints  and  OenotJiera  La- 
marckiana itself. 


IV.    ON  THE  LATENT  CAPACITY  FOR  MUTA- 
TION. 

§  29.   REPEATED  MUTATIONS  ARE  THE  RESULT  OF  THE 

SAME  INNER  CAUSES. 

Hitherto  I  have  confined  myself  to  a  mere  descrip- 
tion of  the  phenomena  of  mutation  in  the  genus  Oeno- 
thera such  as  I  have  directly  observed  them.  .  Our  task 
now  is  to  form  some  idea  of  the  causes  of  these  phe- 
nomena. 

The  attempt  to  deal  with  this  problem  is  not  only  a 
perfectly  legitimate  one  but  the  reader  would  be  justified 
in  complaining  that  my  work  were  incomplete  if  I  did 
not  attempt  to  deal  with  it. 

The  solution  of  this  problem  must,  however,  be  sought 
among  the  facts  themselves.  And  for  this  purpose  I 
shall  divide  my  argument  into  two  parts.  The  causes 
which  can  be  dealt  with  most  easily  are,  naturally,  those 
which  operated  throughout  my  experiment,  that  is  the 
internal  and  external  causes  of  each  of  the  several  muta- 
tions. But  to  provide  an  answer  to  the  questions :  what 
is  the  cause  of  the  whole  phenomenon,  and  to  what  is  the 
initiation  of  the  mutation  period  due  Pisa  task  of  a  very 
different  nature.  And  I  propose  to  postpone  this  to  the 
last  section  of  this  chapter. 


Repeated  Mutations  Due  to  the  Same  Causes.    463 

The  facts,  summarized  in  this  and  tlie  previous  sec- 
tion, of  the  repeated  reappearance  of  the  mutations  ob- 
served in  my  cultures  evidently  admit  of  one  explanation 
only,  viz.,  that  the  potentiality  for  each  mutation  is  pres- 
ent in  a  latent  condition  m  the  apparently  normal  indi- 
viduals in  my  cultures. 

Let  us  take  as  an  example  the  Lamarckiana-id.m\\y 
(p.  224),  of  v^hich  I  have  grov^n  a  great  number  of  suc- 
cessive generations.  The  first  sow^ing  gave  two  mutations 
{lata  and  nanella)  ;  the  following  generation  gave  them 
again,  and  one  other  besides.  The  seeds  for  this  second 
sowing  were  gathered  from  6  seed-parents  which  had 
flowered  far  away  from  other  Oenotheras  and  therefore 
can  only  have  been  fertilized  by  one  another.  They  were 
obviously  chosen  without  any  indication  whether  they 
would  be  more  likely  to  produce  mutations  than  the  re- 
maining individuals  of  the  first  generation.  That  these 
six  seed-parents  reproduced  the  same  mutations  as  their 
parents  proves  that  there  existed  in  them  some  heritable 
character  in  a  latent  condition. 

The  same  is  true  of  subsequent  generations  and  of 
the  other  families  in  my  cultures.  Each  time  the  same 
mutations  arose  from  apparently  normal  individuals.  The 
capacity  for  giving  rise  to  these  must  therefore  have  been 
inherited  in  the  latent  condition. 

If  a  latent  capacity  of  this  kind  is  not  assumed  the 
following  three  facts  become  absolutely  inexplicable. 

First,  the  circumstance  that  the  same  mutation  ap- 
pears in  the  same  crop  in  two  or  more  of  several  indi- 
viduals, whether  the  crop  arises  from  the  seeds  of  one 
or  several  seed  parents. 

Secondly,  the  oft  cited  fact  (Part  II,  p.  272  etc.) 
that  the  appearance  of  mutations  seems  to  depend  almost 


464  On  the  Latent  Capacity  for  Mutation. 

exclusively  on  the  extensiveness  of  the  crop.  Whenever 
I, had  the  opportunity  of  sowing  on  a  large  scale,  either 
with  seeds  from  the  field  at  Hilversum  (1889)  or,  in  my 
own  families,  with  the  seeds  of  a  few  seed  parents,  espe- 
cially in  the  year  1895  (p.  224  and  p.  262),  a  large  num- 
ber of  mutations  appeared.  Their  rarity  in  other  years 
and  cultures  can  therefore  only  be  attributed  to  the  small 
scale  on  which  the  sowings  were  made;  for  on  a  few 
square  meters  we  cannot  expect  to  get  many  mutations 
if  the  seeds  are  not  sown  very  close  and  the  crops  are  not 
examined  every  day. 

Thirdly,  the  small  number  of  the  different  mutations 
which  appeared.  By  no  means  does  every  conceivable 
deviation  occur.  Thus  there  arose  no  white  flowers,  no 
glabrous  or  unbranched  individuals,  no  linear  petals,^  no 
trace  of  petalomany  or  apetaly  and  so  forth.  Even  of 
the  two  new  species  which  w^ere  found  in  the  field  at 
Hilversum,  0.  hrevistylis  and  0.  lacvifolia,  not  a  single 
example  occurred  in  my  cultures. 

We  are  led  to  the  same  conclusion  by  a  consideration 
of  the  more  or  less  incompletely  developed  individuals^ 
of  the  new  species  which  sometimes  seem  to  constitute 
transitional  forms.  For  these  arise  in  my  cultures  not 
before  the  mutants,  but  simultaneously  or  more  com- 
monly only  after  them.  Each  mutation  is  as  completely 
developed  when  it  first  appears  as  afterwards.  When  a 
mutation  is  grown  through  many  generations  and  on 
a  very  large  scale  its  various  representatives  conform 
to  exactly  the  same  type.  I  possess  photographs  and  de- 
scriptions of  my  mutations  from  the  first  year  of  their 
appearance  and  find  that  nothing  has  been  added  to,  or 

^  "Forma  cruciata"  as  found  in  Oenothera  cruciafa  Nuff.  and 
some  others. 


Repeated  Mutations  Due  to  the  Same  Causes.     465 

taken  away  from,  their  type.  I  have  often  hacl  /a/a-plants 
from  two  or  three  sources,  e.  g.,  the  1st,  2d  and  5th  gen- 
erations, growing  side  by  side  in  my  garden;  they  were 
quite  indistinguishable  from  one  another. 

Intermediate  forms  seem  to  be  associated  more  with 
some  mutations  than  with  others.  Rarest  with  O.  nanella, 
they  are  commonest  with  0.  laevifolia.  Sometimes  the 
intermediate  forms  repeat  the  new  type  of  their  species 
more  or  less  completely  in  the  lateral  branches  which 
arise  from  the  axils  of  the  rosette  leaves  (as  for  example 
an  O.  laevifolia  which  exhibited  excessive  crumpling  on 
the  leaves  borne  on  the  main  stem).  In  this  case  they 
may  be  regarded  as  individuals  in  which  the  typical  char- 
acter of  the  species  is  more  or  less  latent  at  first. 

Thus  these  apparent  transitional  forms  are  not  the 
steps  by  means  of  which  the  new  species  has  attained  its 
full  development.  They  are  rather  the  imperfect  copies 
of  a  perfect  picture  which  already  exists.  They  are,  in 
a  word,  the  extreme  variants  of  the  perfectly  constant 
new  type  (see  §§24  and  25). 

It  is  in  this  very  respect  that  the  newly  formed  spe- 
cies behave  in  a  diametrically  opposite  way  to  the  races 
built  up  by  the  accumulation  of  fluctuating  characters 
(Part  I,  §  7,  p.  71)  ;  and  it  is  this  fact  which  justifies 
their  title  to  specific  rank. 

The  general  conclusion  of  this  argument  is : 

At  the  beginning  of  my  observations,  in  the  year  i886, 
the  characters  of  the  nezv  species,  zvhich  appeared  later 
in  my  cultures,  were  already  present  in  the  plants  in  the 
field  at  Hilversum  in  a  latent  condition.  They  remained 
in  that  condition  for  many  generations,  both  there  and  in 
my  cultures,  and  only  appeared  from  time  to  time,  espe- 
cially in  large  sowings. 


466  On  the  Latent  Capacity  for  Mutation. 

I  regard  this  conclusion  as  thoroughly  proved  in  the 
case  of  the  commoner  species  which  appear  in  measur- 
able proportions  (e.  g.,  1%  or  0.1%).  Whether  or  no 
it  also  holds  good  for  the  rarer  ones  or  for  those  which 
did  not  appear  till  late  must  be  regarded  as  of  no  con- 
cern for  the  present. 

But  if  the  existence  of  this  capacity  in  a  latent  con- 
dition in  1886  is  demonstrated  by  my  cultures,  it  follows 
that  all  or  most  of  these  new  species  existed  in  a  latent 
condition  before  that  date. 

This  latent  capacity  to  mutate,  i.  e.,  to  produce  a 
series  of  definite  and  identical  mutations,  is  therefore 
a  heritable  character  in  my  Oenothera  Lainarckiana. 
The  particular  factor  for  every  given  mutation  must  ob- 
viously exist  separately.  And  it  must  be  supposed  that 
the  various  mutations,  although  they  belong  to  the  same 
group  or  period,  are  nevertheless  independent  of  one 
another. 

As  far  as  observation  goes,  this  potentiality  is  always 
inherited  by  all  individuals.  Of  course  many  sowings 
have  given  no  mutants,  and  in  other  sowings  certain 
mutants  have  been  lacking.  But  this  may  always  have 
been  the  result  of  the  smallness  of  the  scale  on  which  the 
experiment  was  carried  out  (whether  this  was  because 
the  available  quantity  of  seed  w^as  insufficient  or  that  a 
small  culture  was  all  that  was  necessary  for  the  imme- 
diate object  of  the  experiment).  In  larger  crops  all  the 
commoner  mutants  appeared  as  a  rule.  For  large  cul- 
tures like  these  the  seeds  of  four  or  even  10-20  seed- 
parents  were  needed.  In  these  cases  I  have  always  sown 
the  seeds  from  each  parent  separately  and  it  has  never 
happened  that  no  mutants  appeared  amongst  the  progeny 


Repeated  Mutations  Due  to  the  Same  Causes.    467 

of  any  single  seed-parent.  If  some  mutants  were  absent, 
others  were  more  numerous  to  make  u])  for  it. 

The  power  to  mutate  is  also  inherited  by  the  new 
species.  We  have  already  seen  several  examples  of  this 
in  §  8  and  later  in  §§  10-23.  For  instance  O.  seiutillaiis 
is  very  mutable:  it  produces  pretty  regularlv  10-207t' 
ohlonga;  about  %%  O.  lata  and  about  %%  0.  nauella 
(p.  244).  O.  ohlonga,  O.  nanella,  O.  leptocavpa  and 
others  gave  also  rise  pretty  regularly  to  the  other  muta- 
tional forms  in  proportions  not  very  different  from  those 
in  which  they  are  produced  by  0.  Lauiarekiana  itself 
(§8).  And  the  same  is  true  of  crosses,  for  example 
between  0.  lata  and  0.  nanclla,  0.  ruhrinervis  and  O. 
nanella  and  so  forth. 

Therefore,  when  a  character  passes  from  it^  latent 
to  its  active  condition,  all  or  apparently  all  of  the  other 
characters  latent  in  it  remain  so.  They  are  not  lost  in 
the  process. 

The  question  arises :  are  they  ever  lost  ? 

0.  hrevistylis  and  0.  laevi folia  seem  to  afford  an 
answer  to  this  question.  They  grew  in  1887  in  the  field 
at  Hilversum,  they  are  not  known  anywhere  else  and, 
what  is  more  to  the  point,  they  have  not  been  observed  as 
mutants  a  single  time  in  my  cultures,  even  in  cultures  of 
many  thousands  of  individuals.  It  is  therefore  possible 
that  they  no  longer  exist  in  my  species  in  a  latent  con- 
dition. 

It  is,  of  course,  possible  that  my  plants  may  not  have 
descended  from  the  same  individual  ancestors  as  those 
from  which  these  two  species  arose.  So  that  my  obser- 
vations do  not  afford  a  definite  proof  that  the  latent  char- 
acters of  these  species  have  been  Jost.  But,  inasmuch  as 
the  whole  lot  of  the  Oenotheras  in  the  wild  locality  has 


468  On  the  Latent  Capacity  for  Mutation. 

only  sprung  from  a  few  individuals,  the  conclusion  that 
they  may  have  been  lost  seems  to  me  very  probable. 

It  is  hardly  possible  to  discover  whether  single  plants 
in  my  cultures  may  sometimes  lose  the  power  of  giving 
rise  to  particular  mutations.  The  negative  results  of 
the  experiments  do  not  enable  us  to  decide.  Far  more 
extensive  cultures  would  be  necessary  to  answer  this 
question  definitely  by  experiment. 

Meanwhile  I  incline  to  the  view  that  the  separate 
latent  characters,  which  become  visible  by  mutation,  may 
be  lost  sooner  or  later. 


§  30.   THE  LATENT  INHERITANCE  OF  OTHER  CHAR- 
ACTERS IN  OENOTHERA  LAMARCKIANA. 

The  foregoing  argument  has  led  us  to  regard  the 
capacity  for  producing  mutations  as  a  latent  heritable 
property.  The  characters  of  the  new  species  exist  po- 
tentially in  the  parent  species  but  remain  invisible  until 
they  are  called  into  active  existence  by  definite  external 
causes.^ 

That  this  hypothesis  bears  strongly  on  the  theory  of 
mutation  and  on  our  whole  conception  of  the  nature  of 
heritable  characters  is  evident.^ 

For  this  reason,  I  have  been  trying  for  many  years 
to  render  the  inheritance  of  latent  characters  accessible 
to  experimental  study,  not  only  in  Oenothera  but  else- 
where. The  best  material  for  this  work  seemed  to  be 
afforded  by  monstrosities  or  teratological  phenomena, 
which  used  to  be  looked  upon  as  something  fortuitous 

'Variabilite  et  Mutabilite,  Rapport  du  Congres  international  de 
botanique,  Oct.  1900,  Paris,  p.i. 

^  See  Intracellulare  Pangenesis,  p.  16,  and  the  second  volume  of 
this  work. 


Other  Characters  in  Oenothera  Lamarckiana.     469 

but  are  now  generally  regarded  as  visiljle  manifestations 
of  a  latent  heritable  potentiality. 

In  the  members  of  certain  families,  (which  may  be 
large  or  small)  the  deviations  in  question  become  visil)le 
so  often,  that  the  presumption  in  favor  of  a  common 
internal  cause  becomes  very  strong.  On  the  other  hand 
the  monstrous  individuals  are  so  frequently  separated 
from  one  another  in  pedigrees  by  perfectly  normal  ones 
that  the  cause,  if  it  is  a  continuous  one,  that  is,  if  it  is 
handed  on  from  one  generation  to  another,  must  be  in- 
operative most  of  the  time.  Finally  the  appearance,  or 
non-appearance,  of  the  monstrosity  in  particular  individ- 
uals is  dependent  on  external  influences  and  mainly  on 
nutritional  conditions.  This  latter  fact  alone  seems  to 
me  sufficient  to  prove  their  presence,  and  consequently 
their  inheritance,  in  a  latent  state. 

Monstrosities  are  much  more  favorable  material  for 
this  purpose  than  mutations.  For  they  are  accessible  to 
everybody,  and  dependent  for  their  appearance  and  de- 
gree of  development  on  their  environment  in  ways  which 
are  easily  investigated.  Except  for  hybrids,  they  afford 
the  best  material  for  studying  and  elucidating  the  general 
principles  of  latent  characters. 

Monstrosities  differ  from  mutations  in  that  their  ap- 
pearance is  partial :  by  this  I  mean  that  they  do  not  affect 
all  the  homologous  organs  of  the  same  plant  but  only 
some  and  usually  very  few  of  them;  whereas  the  muta- 
tions described  in  this  part  are  absolutely  individual. 
Monstrosities  need,  by  no  means,  be  monstrous.  The 
appellation  monstrosity  is  a  very  unfortunate  one;  be- 
cause, in  other  species  many  of  these  teratological  sports 
are  quite  normal  characters.^     As  an  example  I  might 

^  Monstmosites  taxinomiques,  as  they  are  called  by  De  Candolle. 


470  On  the  Latent  Capacity  for  Mutation. 


quote  the  pitchers  or  ascidia,  which  are  analogous  to  the 
peltate  leaves.  It  is  true  that  the  pitchers  often  have  the 
form  of  a  cornet  or  pocket  and  this  restricts  the  assimila- 
tory  capacity  of  the  leaf;  but  that  only  depends  on  the 
form  of  the  normal  leaf  in  the  species  in  question.  If 
the  latter  is  auriculate,  the  pitchers  can  be  quite  or  nearly 
flat,  and  form  per- 
fectly typical  peltate 
leaves ;  for  example  a 
pitcher-forming  Pel- 
argonium zonale  which 
I  have  had  in  cultiva- 
tion for  years  and 
have  propagated  by 
cuttings,  gives  rise, 
every  year,  to  a  num- 
ber of  such  peltate 
leaves  especially  on 
short  shoots.  Simi- 
larly the  first  leaves 
of  the  twigs  of  Tilia 
parvi  flora,  when 
changed  into  ascidia, 
are  almost  absolutely 
flat  (Fig.  106  C). 

I  ought  to  say  that 
my  conclusions  on  the 
mode  of  inheritance  of  monstrosities  are  chiefly  based 
on  species  of  plants  other  than  Oenothera.  They  have 
partly  been  dealt  with  already,^  and  partly  will  be  de- 
scribed in  the  second  volume  of  this  work. 


Fig.  io6.  Tilia  parviiiora.  The  forma- 
tion of  pitchers  from  leaves.  A,  B, 
ordinary  ascidia ;  C,  a  pehate  leaf 
("flat  pitcher")  seen  from  below. 


^  Ueber  die  Erblichkeit  der  Zwangsdrehungen,  Ber.   d.    d.   bot. 
Gesellsch.,  1889,  Vol.  VII,  p.  291 ;  Eine  Methode  Zwangsdrehungen 


Other  Characters  in  Oenothera  Lamarckiana,    471 

But  these  results  agree  so  closely  with  the  facts  re- 
lated here,  that  there  can  be  little  doubt  that  my  general 
conclusion  applies  to  Oenothera  as  well. 

I  have  only  carried  out  a  few  direct  ex]:)eriments 
bearing  on  the  inheritance  of  the  abnormalities  in  Oeno- 
thera Lamarckiana  itself.  They  relate  to  tricotyly  and 
variegated  leaves,  and  will  be  described  in  suljsequent 
sections.  I  have  however  collected  a  fair  number  of  ob- 
servations which  favor  the  argument  for  this  inheritance 
of  latency.  A  series  of  abnormalities  have  occurred  in 
the  plants  in  the  field  at  Hilversum,  as  well  as  in  my 
own  cultures;  some  of  them  seldom,  some  of  them  often; 
but  all  of  them  in  such  a  way  as  to  leave  no  doubt  as  to 
their  heritability.-^ 

The  only  exception  to  this  Is  afforded  by  the  cases  of 
virescence,  which  changes  the  different  parts  of  the  flow- 
ers into  small  green  bracts.  I  never  found  it  on  the 
Oenotheras  at  Hilversum,  and  only  on  one  example  in 
my  own  cultures.  This  was  a  biennial  dwarf  which 
flowered  in  the  summer  of  1890,  and  came  very  near 
bearing  no  seed  at  all  on  account  of  this  abnormality. 
I  regard  this  malformation  as  due  to  the  attack  of  some 

aiifzusuchen,  ibid.,  1894,  Vol.  XII,  p.  25 ;  Uehcr  halbc  Galton-Curvcn, 
ibid.,  1894,  Vol.  XII,  p.  197;  Monographie  dcr  Zwangsdrchungen  in 
Pringsh.  Jahrb.  f.  wiss.  Bot.,  Vol.  XXIII,  p.  14  and  Over  dc  crfclyk- 
heid  van  fasciatien,  Kruidkundig  Jaarboek,  Gent,  1894,  IV  Jaargang, 
p.  72. 

*  For  the  inheritance  of  monstrosities  see :  Erf  dyke  Moustrosi- 
teiten,  Kruidkundig  Jaarboek  Dodonaea,  1897,  p.  62 ;  Over  de  crfelyk- 
heid  van  Synfisen,  ibid.,  1895,  p.  129;  Sur  la  pcriodicite  des  anomalies 
dans  les  plantes  monstrueuses,  Archiv.  Neerl.  d.  Sc.  exactes  et  nat., 
Serie  II,  Tome  III,  p.  371  ;  Ueber  die  Abhangigkeit  dcr  Faseiation 
vom  Alter  bei  zweij'dhrigen  PHanzen,  Botan.  Cenlralbl.,  Vol.  yy,  1899; 
On  Biastrepsis  in  its  Relation  to  Cultivation,  Annals  of  Botany,  1899; 
Vol.  XIII,  No.  51,  p.  395;  Sur  la  culture  des  nionstruosites,  Comptes 
rendus  de  I'Acad.  d.  Sc,  Paris,  Janv.  1899;  Sur  la  culture  des  fascia- 
tions  des  especes  annuelles  et  bisannuelles;  Revue  gcnerale  de  Bo- 
tanique,  T.  XI,  1899,  p.  136;  Erndhrung  und  Zuchtivahl,  Biol.  Cen- 
tralblat,  Bd.  XX,  No.  6,  1900,  p.  193. 


472  On  the  Latent  Capacity  for  Mutation. 

disease,  analogous  to  those  cases  in  which  parasites  have 
been  observed  as  the  causes  of  virescence.^ 

Monstrosities  often  differ  from  ordinary  individual 
variations  in  the  fact  that  they  are  deviations  on  one  side 
only  of  the  type  of  the  species,  whilst  the  latter  deviate 
from  both  sides  of  the  mean.  In  this  way  we  get,  when 
we  have  a  sufficient  number  of  instances  of  the  same 
monstrosity  in  a  given  species,  the  socalled  half-Galton 


Fig.  107.  Oenothera  Lamarckiana.  Fruit  in  the  axil  of  a 
deeply  split  double  leaf;  the  flower  from  which  this  fruit 
arose  had  the  double  number  of  sepals  and  petals  and 
stamens  as  a  normal  flower,  and  was  elongate  in  trans- 
verse section. 

curves.^  Polymerous  flowers,  5-9  partite  fruits,  split 
stigmas  and  even  fasciation,  all  illustrate  the  same  law.^ 
But  the  majority  of  monstrosities  are  much  too  rare  to 

"^  Een  epidemie  van  vergroeningen,  Kruidkundig  Jaarboek,  Gent, 
T.  VIII,  1896,  p.  66. 

^  Berichte  d.  deutsch.  Bot.  Gesellsch.,  Bd.  XII,  1894,  p.  197-207, 
with  Plate  X. 

^  See  Sur  les  courhes  Galtoniennes  des  monstruosiies,  Bull.  Scien- 
tif.  de  la  France  et  de  la  Belgique  public  par  A.  Giard^  T.  XXVII, 
p.  396,  Avril  1896. 


Other  Characters  in  Oenothera  Lamarckiana.     473 

afford  material  for  statistics  of  this  kind  unless  we  breed 
them  for  the  purpose.  I  shall  give  an  account  of  some 
isolated  observations  which  will,  I  hope,  incite  others  to 
further  investigation  in  this  field. 

In  Penzig's  excellent  work  on  Teratologv  (Vol.  I, 
p.  481)  the  whole  genus  Oenothera  takes  up  only  about 
half  a  page.  Our  O.  Lamarckiana  is  not  mentioned  there 
and  of  course  no  monstrosities  of  it  are  described.  The 
account  of  the  abnormalities  of  O.  biennis,  however,  is  im- 
portant from  our  point  of  view.  This  plant  exhibits  an 
extraordinary  tendency  to  fasciation  and  often  gives  rise 
to  pentamerous  flowers  and  5-9  partite  fruits.  I  can 
confirm  these  statements  from  numerous  observations  of 
my  own ;  I  also  found  the  number  of  stigmas  varying  in 
the  same  way  as  in  Lamarckiana.  Clos  cites  a  pistil 
divided  into  seven  in  O.  campylocalyx  (ibid.),  and  syn- 
anthy  in  Oenothera  has  been  mentioned  by  Masters  (see 
also  Fig.  107). 

Just  as  in  O.  biennis,  the  chief  constituents  of  the 
monstrosities  presented  by  the  Oenotheras  growing  in 
the  locality  near  Hilversum  and  by  the  families  derived 
from  them  in  my  cultures,  are  fasciations,  pentamerous 
and  polymerous  flowers,  5-9  partite  fruits,  and  an  in- 
creased number  of  stigmas.  These,  together  with  varie- 
gation of  leaves  and  tricotyly  in  seedlings,  which  occur 
in  other  Oenotheras  as  well,  are  the  common  abnormal- 
ities; the  rest,  in  my  experience,  are  relatively  rare.  I 
shall  therefore  divide  the  various  instances  into  two 
groups,  the  common  and  the  rare  ones. 

The  rare  monstrosities  were  tolerably  well  repre- 
sented in  the  locality  at  Hilversum,  as  compared  with 
other  wild  plants.  This  was  one  of  the  causes  of  the 
lively  impression  which  the  great  degree  of  variability 


474  On  the  Latent  Capacity  for  Mutation. 

of  this  plant  made  on  me  at  first.  I  was  at  first  inclined 
to  regard  this  phenomenon  as  local,  like  the  actual  muta- 
tions, but  had  no  opportunity  to  institute  an  investiga- 
tion of  the  matter.  Perhaps  other  observers  in  other 
places  will  be  able  to  fill  up  these  gaps.  The  chief  point 
for  my  purpose  is  the  proof  that  a  high  degree  of  her- 
itable variability  was  actually  in  existence  in  the  plants 
in  the  field  at  Hilversum. 

Tricotyly.^  Tricotylous  seedlings  are  fairly  abundant 
in  my  cultures;  hemitricotyly,  which  simply  consists  in 
the  splitting  of  one  of  the  cotyledons,  is  somewhat  rarer. 
I  have  onlv  recorded  these  two  abnormalities  occasion- 

ml 

ally,  as  compared  with  the  others,  because  I  regarded 
them  as  of  little  importance  at  first.  The  following 
summary  of  the  cases  noted  will  however  give  data  as 
to  their  occurrence  and  frequency  in  the  different  fam- 
ilies. 

I  have  started  three  experiments  on  the  inheritance 
of  these  abnormalities  by  sowing  seeds  of  tricotylous 
plants  in  three  different  families,  of  0.  nanella,  0.  laevi- 
folia  and  0.  ruhrinervis :  in  the  latter  only,  however,  was 
the  experiment  continued  through  subsequent  genera- 
tions. 

In  the  following  summary  the  years  refer  to  the  seed- 
lings and  not  to  the  parent  plants  of  the  preceding  har- 
vest. 

In  1887  I  got  tricotyls  from  seeds  collected  at  Hilver- 
sum; one  of  them  grew  up  as  an  0.  lata,  but  set  no  seed. 

In  1890  I  found  one  tricotylous  seedling  in  the  chief 
strain  of  the  Lamar ckiana-i^mWy  (p.  224),  and  in  a  crop 
of  one  of  its  wa^^j/Za-subfamilies :  the  latter  grew  up  as 
a  dwarf. 

^  See  also  the  second  volume. 


Other  Characters  in  Oenothera  Lamar ckiana.    475 

In  1890  I  got  two  tricotyls  in  the  LaevifoUa-i^.m\\y 
(p.  273).  In  the  spring  of  1892  I  sowed  the  seeds  of  the 
previous  harvest  on  a  large  scale  in  the  greenhouse  of 
my  laboratory.  I  searched  for  the  tricotyls  amongst 
the  many  thousands  of  seedlings,  and  planted  them  out 
in  pots  in  May.  There  were  71  of  them.  Of  these,  63 
set  seed  in  the  same  year;  the  seed  of  each  plant  was 
harvested  separately  and  sown.  In  this  crop  I  counted 
(March  1893)  the  tricotyls  in  100-200  seedlings  for 
every  seed-parent.  Altogether  I  looked  through  over 
13,000  seedlings,  and  found  amongst  them  about  1% 
tricotyls  on  the  average.  The  proportions  amongst  the 
individual  seed-parents  varied  between  0  and  2%  ;  only 
five  contained  more ;  in  these  the  proportions  of  tricotyls 
were  2.5 — 2.7 — ?>.2> — 3.4  and  3.8%.  Occasional  hemi- 
tricotyls  were  discovered  in  this  extensive  experiment, 
and  a  single  syncotyl.  Nothing  was  transplanted  from 
this  crop. 

I  found  a  tricotylous  plant  of  O.  nanella  in  1889, 
when  0.  nanella  first  appeared ;  in  1892  I  also  found  three 
tricotyls  in  this  race,  which  was  well  established  by  this 
time :  they  all  remained  dwarf,  and  set  seed.  In  April 
1893  these  seeds  gave  four  tricotyls  in  800  seedlings, 
i.  e.,  0.5%,  and  one  hemitricotyl  besides.  The  tricotyls 
grew  up  as  dwarfs ;  the  hemitricotyl  was  not  planted  out. 

In  1890  I  found  one  tricotyl  in  the  sowing  of  the 
/aia-family  of  that  year  (p.  288). 

In  1890  I  also  found  one  hemitricotyl  in  the  rubrincr- 
T'W-family  (p.  273),  a  single  tricotyl  in  1891,  and  numer- 
ous tricotyls  in  the  larger  crops  that  were  raised  in  1892. 
From  these  latter  I  have  since  formed  a  tricotylous  sub- 
family which  I  still  cultivate,  without,  however,  being- 
able  to  increase  the  percentage  of  tricotyls  to  a  better 


476  On  the  Latent  Capacity  for  Mutation. 

amount.  In  1892  I  had,  besides  20  tricotyls,  6  henii- 
tricotyls  which  however  I  did  not  cultivate  further.  The 
seeds  of  each  of  the  former  was  harvested  separately 
and  sown;  the  best  of  them  gave  2.6 — 2.8%  tricotyls, 
but  the  majority  less  than  1.5%.  The  proportion  in  8000 
seedlings  was  0.7% ;  there  were  also  7  hemitricotyls  and 
2  syncotyls. 

In  1893  I  planted  out  70  seedlings  derived  from  five 
seed-parents  which  had  given  from  1.5  to  2.8%  tricotyls. 
In  1894,  however,  they  yielded  a  harvest  in  which  the 
percentage  was  very  low,  having  sunk,  in  the  case  of  the 
best  seed-parents,  to  1%.  I  planted  out  about  90  of  the 
best  seedlings,  with  a  view  to  obtaining  seed  from  them. 
Besides  the  above  mentioned  tricotyls  in  the  crop  of  1894, 
I  found  several  hemitricotyls  and  a  single  tetracotyl ; 
also  a  considerable  number  of  syncotyls  and  one  amphi- 
syncotyl  or  seedling  with  the  cotyledons  fused  together 
on  both  sides. 

This  brief  resume  suffices  to  show  that  tricotyly  is 
heritable  and  that,  in  my  families,  it  is  transmitted  from 
generation  to  generation  even  through  plants  with  normal 
cotyledons,  i.  e.,  in  a  latent  state. 

Fasciation.  Split  and  fasciated  stems  occur  almost 
every  year  in  my  Oenothera  Lamarckiana.^  The  ab- 
normality usually  occurs  in  the  axis  of  the  inflorescence ; 
very  rarely  lower  down  in  the  stem  or  in  the  rosette. 
Fasciated  plants  occurred  in  all  my  families  with  a  few 
inconsiderable  exceptions ;  but,  as  far  as  possible  I  never 
chose  them  as  seed-parents. 

The  "split  stem"  is,  so  to  speak,  the  lowest  stage  in 
the  development  of  this  abnormality,  and,  consequently, 

^  Over  de  crfelykheid  van  fasciatien,  in  Botanisch  Jaarboek  Do- 
donaea  VI,  1894,  pp.  92  and  95. 


Other  Characters  hi  Oenothera  Lamarckiana.    A77 

the  commonest.  In  the  first  years  of  my  observations 
in  the  field  I  made  careful  notes  on  the  mode  of  fascia- 
tion.  There  were  20  cases.  Of  these  14  had  split  stems 
(of  which  one  was  split  twdce)  ;  5  formed  narrow 
''bands,"  and  in  only  one  of  them  was  the  top  of  the  stem 
really  broad.  These  figures  are  sufficient  to  show  that 
the  distribution  of  the  frequencies  of  the  various  degrees 
of  development  of  this  abnormality  will  form  a  half 
Galton-curve. 

I  first  found  fasciations  in  the  field  at  Hilversum 
1886,  in  a  flowering  plant  and  in  a  dead  one  of  the  ])re- 
vious  year  (1885).  I  found  them  again  in  1887,  1888, 
1889,  1892  and  1893 — altogether  15  cases,  which  were 
all  found  in  one  and  the  same  corner  of  the  field.  In 
1894  the  fasciations  were  much  more  numerous  and  scat- 
tered over  the  whole  field ;  I  myself  observed  six  cases ; 
further  ones  were  observed  by  others.  I  observed  two 
cases  of  fasciation  in  1888  in  a  garden  which  I  had  then 
at  Hilversum :  one  was  a  plant,  which  I  had  raised  from 
a  seed  which  had  given  rise  to  a  tricotyl  in  1887,  and  had 
a  stem  which  split  twice  successively ;  the  other  was  a  case 
of  fasciation  of  a  three-year-old  plant  which  was  planted 
as  a  rosette  in  the  garden  in  1887. 

In  1894  I  found  an  example  of  O.  brevisfylis  with  a 
narrow  fasciation  and  a  case  in  O.  laevifolia  was  also 
brought  to  me. 

In  my  cultures  the  following  cases  occurred.  I  had 
three  cases  in  the  Laniarckiana-i?iVL\\\y  (p.  224)  in  two 
annual  dwarfs  in  1888  and  1890  respectively;  neither  of 
them  were  grown  to  maturity.  In  1889  there  occurred 
in  this  family  a  biennial  plant  of  0.  lata  which  bore  two 
split  lateral  twigs.  Fasciation  also  occurred  in  the  lata- 
family  itself  (p.  285),  but  not  until  the  third  generation 


478  On  the  Latent  Capacity  for  Mutation. 

in  the  year  1894  in  which  three  of  the  sixteen  individuals 
that  were  grown  showed  signs  of  spHtting  in  the  quite 
young  rosettes;  two  of  these  developed  strong  and  tall 
flowering  stems.  The  fasciation  repeated  itself,  here  and 
there,  on  these  plants. 

In  my  later  cultures  (1895-1900)  fasciation  grad- 
ually came  to  show  a  predilection,  so  to  speak,  for  two 
distinct  periods  on  the  life  of  the  plant.  First  for  the 
seedling  stage.  In  this  case  the  axis  divides  either  above 
the  cotyledons,  or  above  the  first  two  leaves.    There  arise 


Fig.  io8.  Oenothera  Lamarckiana.  A  double  rosette  of 
radical  leaves  at  the  beginning  of  July.  The  cotyledons 
are  still  on. 

in  this  way  two  rosettes,  whose  leaves  intertwine  because 
of  the  closeness  of  the  two  axes  to  one  another.  In  the 
plant  figured  in  Fig.  108  I  have  bent  the  two  axes  apart 
and  separated  the  two  groups  of  leaves  as  much  as  pos- 
sible before  photographing  it,  in  order  to  make  the  figure 
clearer.  When  a  plant  like  this  grows  up  it  usually  has 
two  equall}^  strong  stems  which  attain  the  same  height 
and  begin  to  flower  at  the  same  time.     I  have  only  arti- 


Other  Characters  in  Oenothera  Lamarckiana.    479 

ficially  fertilized  such  plants  when  it  happened  to  be  ne- 
cessary to  record  the  progeny  of  all  the  plants  on  the  bed 
on  which  it  stood.  Otherwise  I  have  suppressed  them, 
so  as  not  to  load  the  cultures  with  plants  of  this  incon- 
venient form. 

Double  rosettes  of  the  sort  figured  have  appeared  al- 
most every  year  since  the  beginning  of  my  experiment 
and  very  often  in  large  numbers.  I  found  most  of  them 
in  0.  Lamarckiana,  but  also  in  O.  lata,  O.  nanella,  0.  Jiir- 
tella,  etc. 

The  second  period  of  the  life  of  the  plant  in  which 
fasciations  are  commonest  occurs  in  autumn.  If  we 
allow  the  main  stem  to  go  on  flowering  till  autumn  its 
top  often  broadens  out. 

But  most  of  the  plants  in  my  cultures  have  stopped 
flowering  by  that  time.  Those  which  have  been  recorded 
and  are  not  wanted  for  other  reasons  are  weeded  out, 
seed  plants  are  decapitated,  and  plants  fertilized  by  in- 
sects are  so  heavily  laden  with  fruits  that  flowering  ceases 
of  its  own  accord.  But  O.  hrcvistylis  is  very  suitable  in 
this  respect,  because  it  practically  bears  no  fruit  and  sets 
no  seed;  a  character  by  which  it  is  easily  recognizable 
even  when  flowering  is  over.  I  have  often  allowed  a 
whole  bed  of  this  species  to  go  on  flowering  into  Novem- 
ber; with  the  result  that  the  top  of  many  of  the  plants 
began  to  broaden  out  either  in  September  or  October, 
and  so  quickly  that,  in  a  very  few  weeks,  it  attains  a 
breadth  of  1-2  cm.  The  fan-shaped  tops  of  the  stems 
were  often  as  broad  as  they  were  long.  As  to  their  fre- 
quency, I  had,  for  example,  in  1898,  20  fasciated  indi- 
viduals in  a  bed  of  49  flowering  plants  of  O.  brez'isfylis: 
that  is  about  40%  ;  and  in  another  culture  of  the  same 
species  63  fasciated  and  11  not;  that  is  about  70%. 


480  On  the  Latent  Capacity  for  Mutation. 

Other  new  and  old  species  were  also  much  subject  to 
fasciatlon.  For  example  in  October  1899  they  were  par- 
ticularly numerous  in  0.  hirtclla  and  some  of  its  hybrids ; 
many  occurred  amongst  0.  lata  and  0.  albida  in  1897; 
and  amongst  0.  nanella  in  1895.  In  one  culture  of  O. 
muricata  in  1896  there  were  as  many  as  80%.  fasciated 
individuals;  and  in  the  cross  O.  muricata  X  0.  biennis 
30%  in  1896  and  25%  in  1898;  and  so  forth. 

These  and  other  observations,  not  worth  printing, 
made  in  the  garden  and  the  field,  seem  to  me  to  warrant 
the  conclusion  that  the  capacity  to  produce  fasciations 
under  suitable  circumstances  is  heritable  in  a  latent  con- 
dition in  the  genus  Oenothera  or  at  least  in  the  group  of 
the  bicnnis-speciQS   (subgenus  Onagra). 

Variegation  of  leaves.  I  only  very  seldom  found 
plants  with  yellow  edged  leaves — the  first  time  was  in 
1887;  otherwise  the  variegated  leaves  were  streaked  in 
the  ordinary  way.  I  found  two  of  these  at  Hilversum 
in  1887  and  two  again  in  1893;  I  sowed  the  seeds  of 
the  former  and  got  a  single  variegated  plant  amongst 
m.any  green  ones  in  1888.  Some  seeds  collected  at  Hilver- 
sum in  1888  gave  one  annual  variegated  plant. 

This  abnormality  also  appeared  in  my  cultures  from 
time  to  time.  For  example  in  the  /a/a-family  in  1888, 
1890  and  1899;  in  the  laez'ifolia-immly  in  1889  (6  ex- 
amples), 1891,  1894  and  1899.  In  the  riibrinej'Z'is-iRmUy 
in  1893  and  1894,  in  O.  nanella  in  1899  and  amongst  the 
scintillans  of  1890. 

The  Lamarckiana-i3.mi\y  gave  two  in  1888  and  two 
in  1890;  the  first  two  were  annual  and  set  seed,  from 
which  I  got  a  fair  number  of  beautifully  variegated 
rosettes  in  the  following  year  1889. 

In  the  rubrinervis-idiVcnly  there  were  occasional  cases 


Other  Characters  in  Oenothera  Lamarckiana.    481 

of  an  absolutely  yellow  seedling.  These  seedlings  appar- 
ently contain  no  chlorophyl  and,  therefore,  die  after  tlie 
unfolding  of  the  cotyledonary  leaves.  It  is  worth  while 
going  into  this  case  a  little  more  closely.  Of  the  tricot- 
ylous  riibri}ie7'vis-p\2ints  whose  seeds  had  been  collected 
separately  in  1892  there  were  several  which  gave  rise  to 
occasional  yellow  seedlings.  One  parent  plant  was  par- 
ticularly fertile  in  this  respect.  It  gave  rise  to  498  seed- 
lings of  which  95  were  absolutely  yellow  and  3  had  varie- 
gated cotyledons.  The  rest  were  pure  green ;  these  grew 
well,  whilst  the  yellow  ones  died  young.  The  proportion 
of  yellow  and  variegated  individuals  was  therefore  20%  : 
and  these  abnormal  seedlings  soon  perished.  Of  the 
green  ones  I  kept  64,  some  of  them  till  they  ripened  their 
fruits,  but. none  of  them  showed  any  signs  of  variegation. 

Inasmuch  as  variegated  plants  were  never  chosen  as 
seed-parents  (except  in  special  experiments  devoted  to 
that  character)  and  were  usually  destroyed  before  they 
flowered,  it  follows  from  these  observations  that  this  ab- 
normality is  not  only  heritable  but  is  maintained  in  the 
various  families  in  a  latent  state  from  generation  to  gen- 
eration. 

Variegated  plants  occurred  from  time  to  time  in  other 
cultures  than  those  of  O.  Lamarckiana  itself,  as  I  have 
already  stated.  They  also  occurred  amongst  the  result 
of  crosses  between  O.  Lamarckiana  and  its  subspecies, 
and  between  this  and  the  older  species.  But  the  details 
of  these  observations  are  not  worth  printing. 

Polymery  in  the  flowers  has  not  been  a  rare  phenom- 
enon at  Hilversum  during  my  acquaintance  with  the 
spot.  Whenever  I  examined  a  large  number  of  flowers 
I  usually  found  at  least  one  polymerous  one.  This  was 
also  the  case  in  my  cultures.     In  the  first  years  of  my 


482  On  the  Latent  Capacity  for  Mutation. 

experiments  I  recorded  about  30  polymerous  flowers 
partly  in  the  field  and  partly  in  my  laevifolia-isimily.  Be- 
low is  a  summary  of  these  cases,  giving  also  the  date  and 
place  or  family  in  which  they  occurred.  The  numbers 
of  stigmas  is  noted  separately  (N),  but  the  number  of 
divisions  of  the  fruit  (O)  have  been  omitted  in  some 
cases. 


MBE 

R       FORMULA 

DATE 

LOCALITY 

1 

K4C5S8N5O4 

1887 

Hilversum. 

1 

K4C5S8N6O4 

1887 

( ( 

1 

K4C5S9 

1894 

laevifolia. 

1 

K4C5S10N6O4 

1888 

Hilversum. 

1 

K4C6S10N8 

1887 

laevifolia. 

1 

K4C4iS8N505 

<i 

Hilversum. 

1 

K4C4^Sl0N8O5 

{( 

<( 

1 

K5C5S9N7O5 

(( 

iC 

1 

K5C5S10N4O5 

(( 

(( 

3 

K5C5S10N5O5 

(( 

(( 

1 

K5C5S10N5O5 

1888 

From  seeds  from 
Hilversum. 

2 

K5C5S10 

1886, 1887 

Hilversum. 

1 

K5C5S10 

1890 

laevifolia. 

4 

K5C5S10N6O5 

1887 

Hilversum. 

1 

K5C5S10N6O5 

1894 

laevifolia. 

4 

K5C5S10N7O5 

1887 

Hilversum. 

1 

K6C4iSl0N8O6 

(( 

(( 

1 

KeCsSnNsOe 

(< 

(< 

1 

K6C6S12N8O6 

<( 

(( 

1 

K6C7S12N8O5 

(( 

(( 

1 

K7C7S14N7O7 

(C 

<( 

1 

K7C7Si4Nn 

1890 

laevifolia. 

Even  from  the  above  incomplete  summary  it  is  suf- 
ficiently evident  that  the  distribution  of  the  frequencies 
of  these  anomalies  would  give  half-Galton-curves.     In 


Other  Characters  in  Oenothera  Lamarckiana.     483 

the  first  place,  I  have  never  seen  fewer  than  four  sepals 
or  petals  or  divisions  in  the  ovary,  and  never  fewer  than 
8  stamens.  The  variation  is  solely  on  one  side :  at  any 
rate  it  has  been  so  during  the  nine  years  covered  by  the 
above  mentioned  observations,  and  since  then  as  well. 
Trimerous  flowers,  which  could  hardly  escape  the  atten- 
tion of  even  the  most  superficial  observer,  are  certainly 
not  present.^  The  'half  Galton-curves'  are  obtained  by 
considering  variability  of  sepals,  petals,  etc.  separately. 

For  the  sepals : 

21  Ks  4  Ke  2  K7  Total,  27  flowers. 
For  the  petals : 

23  C5         3  Ce  3  C7  Total,  29  flowers. 

For  the  partitions  of  the  fruit : 

18  O5         3  Oe  1  O7  Total,  22  fruits. 

I  have  often  seen  pentamerous  fruits,  not  only  at 
Hilversum  but  in  my  own  cultures.  They  were  especially 
common  in  O.  Lamarckiana  and  O.  laevi folia ;  but  I  have 
seen  them  in  the  other  species  as  well.  I  have  rarely 
seen  6-  and  7-partite  fruits,  and  8-partite  ones  never, 
so  far. 

The  curve  for  the  stamens  in  the  above  table  turns 
out  somewhat  differently: 

2  S9     21  Sio     1  Sii     2  S12     2  Si4    Total,  28  flowers. 

But  we  must  bear  in  mind  that  the  numbers  of  sta- 
mens are  usually  even.  Now  if  we  omit  the  odd  num- 
bers, as  we  did  with  the  split  petals,  we  get  a  beautiful 
half-Galton-curve :  21  Sio  —  2Si2  —  2Si4. 

^  In  O.  biennis  T  sometimes,  though  very  rarely,  found  trimerous 
and  even  bimerous  flowers.  I  have  also  seen  some  in  my  hybrid 
cultures.  See  also,  A.  Weisse,  on  O.  biennis  (K3  Ca  So  Go)  in 
Verhandl.  Brandenb.  Jahrg.  39,  1897,  p.  XCIV  with  figure. 


484  On  the  Latent  Capacity  for  Mutation. 

The  stigmas  behave  in  exactly  the  same  way: 

6  Ns      7  Ne      5  Ns     1  Nu      Total,  19  flowers. 

This  curve  would  have  to  be  reduced  in  the  same 
manner.  An  increased  number  of  stigmas  (or  of  the 
divisions  of  the  stigmas)  is  however  so  common  in  ordi- 
nary tetramerous  flowers  that  the  above  cases  are  insig- 
nificant compared  with  them.  Flowers  with  5-8  stigmas 
are  common ;  and  as  a  rule  all  or  most  of  the  flowers  on 
a  single  plant  have  these  high  numbers ;  but  I  very  rarely 
found  flowers  with  9,  10  and  11  stigmas.  The  variation 
in  the  number  of  stigmas  is  therefore  also  describable  by 
a  half  Galton-curve. 


Fig.  log.  Oenothera  Lamarckiana.  Pitcher  formation  on  a 
fasciated  plant,  1892.  The  pitcher  is  inserted  close  to 
the  base  of  the  lower  leaf;  but  more  than  half  of  its 
stalk  is  fused  to  the  main  stem. 

The  tendency  of  the  parts  of  the  flower  to  polymery 
has  therefore  been  latent  in  Oenothera  Lamarckiana  and 
in  the  various  families  during  the  whole  period  of  my 
investigations. 

Some  Rarer  Partial  Deviations  on  Vegetative  Parts. 

Leaves  with  two  apices  and  split  median  veins  oc- 
curred in  1887  and  1888  on  the  field  at  Hilversum,  in 
1887  in  a  tricotylous  O.  lata,  in  1892  in  a  tricotylous  0. 
laevifolia,  and  repeatedly  since  in  the  various  cultures. 


Other  Characters  in  Oenothera  Lamarckiana.     485 

Pitcher  formation  came  under  my  notice  ten  times 
altogether,  in  1887  and  1892  in  the  field  at  Hilversiim, 
in  1889  and  later  in  my  own  cultures.  The  first  two 
pitchers  occurred  on  fasciated  stems  (Fig.  109),  the 
third  on  an  0.  lata,  two  on  O.  laevifolia  (1891,  1895), 
two  on  0.  alhida  (1898),  two  on  O.  Lamarckiana 
(1891,  1895),  and  one  on  O.  nanella  (1897).  In  these 
cases  the  pitcher  usually  took  the  place  of  a  leaf  about 
the  middle  of  the  stem  when  the  plant  was  in  flower, 
that  is  to  say  below  the  inflorescence;  but  the  point  of 
attachment  to  the  stem  always  seemed  to  have  been  dis- 
placed upward.  The  pitchers  were  small,  usually  from 
1  to  3  centimeters  long;  their  dorsal  side  being  usually 
three  times  as  long  as  the  ventral.  They  were  set  on  long 
thin  stalks  about  3  centimeters  in  length. 

Pitcher  formation  was  also  observed  in  the  first  leaves 
of  young  seedlings.  Ascidia  also  occurred  in  0.  biennis, 
in  0.  Lamarckiana  X  biennis  (1896)  and  O.  Lamarck- 
iana X  suaveolens  (1897).  In  1897  I  found  in  a  fairly 
small  culture  of  0.  hirtella  five  young  plants  with  a 
pitcher  on  the  top  of  the  stem  which  interfered  with  the 
flowering  of  the  main  shoot. 

This  repeated,  though  rare,  appearance  of  the  phe- 
nomenon, scattered  as  it  is  pretty  evenly  over  the  various 
families,  points  to  the  conclusion  that  it  is  inherited  in 
a  latent  state.  ^ 

Concrescence  of  two  successive  leaves  on  the  stem 
also  occurred,  though  rarely :  I  first  saw  it  in  1887.  Syn- 
anthy  in  the  axils  of  leaves  which  had  become  concrescent 
or  at  any  rate  grown  too  close  together,  sometimes  oc- 

^  Over  de  erfelykheid  van  Syntisen,  Kruidkundig  Jaarboek  Do- 
donaea;  T.  VII,  p.  129;  for  Oenothera  see  p.  165. 


486  On  the  Latent  Capacity  for  Mutation. 

curred,  forming  structures  which  looked  hke  fine  double 
flowers. 

A  leaf  was  sometimes  fused  longitudinally  with  the 
stem,  with  the  result  that  that  part  of  the  stem,  to  which 
the  leaf  was  attached,  was  checked  in  its  growth  and  bent 
in  a  most  remarkable  fashion.  I  observed  a  case  of  the 
concrescence  of  an  axillary  shoot  with  the  main  stem 
in  1899. 


Fig.  1 10.  Oenothera  ruhrinervis.  A  flower  with  two  bracts; 
the  lower  one,  the  larger  of  the  two,  on  the  fruit  pedicel, 
the  upper  on  the  fruit  itself.  The  bract,  in  the  axil  of 
which  the  flower  arose,  is  not  shown. 


Rarer  partial  variations  in  the  flowers.  A  leafed  and 
stalked  fruit  occurred  in  the  tricotylous  culture  of  the 
O,  riibrinervis-isimily  (Fig.  110).  The  stalk  was  7  milli- 
meters long  and  bore  a  leaf  (a)  whose  median  axis  coin- 
cided with  that  of  the  bract  in  whose  axil  the  flower 
arose.  This  leaf,  which  was  situated  on  the  side  of  the 
main  bract  was  7  cm.  long  and   1.5  cm.   broad.     The 


Other  Characters  in  Oenothera  Lamarckiana.    487 

second  leaf  was  inserted  about  in  the  middle  of  the 
length  of  the  capsule  on  the  somewhat  concave  side  of 
it,  facing  the  main  stem;  it  was  quite  small  (b),  being 
only  2  cm.  long  and  4  cm.  broad.  Bract  and  flower  were 
otherwise  quite  normal.^ 

The  existence  of  two  flowers  (and  their  fruits)  in  the 
axil  of  a  single  leaf  is  a  very  rare  phenomenon.  When 
it  occurs,  the  upper,  much  larger,  flowei  of  the  two  is 
to  be  regarded  as  the  normal  one,  whilst  the  lower, 
smaller  one,  which  flowers  much  later  must  be  supposed 
to  arise  as  an  accessory  bud  (Fig.  111).  Whether  this 
supernumerary  flower  is  to  be  regarded 
as  a  shoot  arising  in  the  axil  of  a  leaf 
which  has  remained  undeveloped  but 
corresponds  in  its  position  to  the  above 
described  supernumerary  leaf  must  re- 
main for  the  present  unsettled.^ 

I  observed  this  case  of  serial  axillary  Fig.  in.  Ocno- 
ui  j_        1  ^1       /-ii.TT-i  tliera     Lamar  ck- 

Duds  not  only  on  the  held  at  Hnversum      iana.  Two  fruits 

(1887)  but  also  in  my  cultures,  viz.,  in      j"  i^%^f'''\  °^  ^ 

^  ^  .  ,        -^  .       ;  '  leaf.    The  lower, 

O.  Lamarckiana,  in  O.  laevifolia  and  in  outer  one  is  the 
one  or  two  other  new  species  and  crosses.  ^'^""ses . 
In  the  latter  they  were  particularly  numerous  in  1900. 
The  free  tips  of  the  sepals  are  sometimes  broadened 
and  take  on  the  form  and  color  of  a  leaf.  I  observed 
this  in  my  cultures  of  1889,  1894,  and  later.  The  sepals 
themselves  may,  on  the  one  side,  assume  the  character 
of  a  petal  (1889).  The  petals  themselves  sometimes 
have   outgrowths  projecting   from    their    median    axes 

*  It  is  perhaps  not  superfluous  to  recall  the  fact  that  Ocuothcra 
has  no  prophylls  (Eichler,  Bliithendiagrammc,  II.  458)  and  that 
normal  prophylls  are  inserted  not  medianly,  but  laterally. 

^Russell,  Recherches  sur  les  bourgeons  multiples,  Annales  des 
Sc.  nat.,  7  Serie,  T.  VII. 


488  On  the  Latent  Capacity  for  Mutation. 


(1887).  Cases  are  not  rare  in  which  supernumerary 
petals  are  formed  by  the  transformation  of  one  longi- 
tudinal half  of  a  stamen  into  that  of  a  petal.  I  found 
cases  of  this  at  Hilversum  in  1886  and  1887,  and  after- 
wards in  my  cultures.  Usually  only  one  such  organ  is 
present  in  a  flower  but  sometimes  more,  and  once  I  ob- 
served as  many  as  four  (1894).  There  also  occurred 
stamens  which  took  on  the  form  of  petals  by  both  the 
filament  and  the  anther  becoming  flattened  (1887,  1888 
and  later  in  the  cultures).     Cases  of  the  fusion  of  two 


-5iSi 


Fig.  112.  Oenothera  Lamarck- 
iana.  Buds  in  the  forks  of  split 
cotyledons. 


Fig.  113.  Oenothera  Lamarck- 
iana.  Bud  in  the  fork  of  a  split 
cotyledon.  The  bud  has  grown 
up  to  a  strong  lateral  rosette; 
its  base  has  much  swollen  in 
consequence. 


filaments  together,  and  of  the  fusion  of  a  filament  with 
the  pistil  are  fairly  rare.  I  observed  the  former  in  1887, 
the  latter  in  1894. 

As  the  foregoing  summary  shows,  the  common  floral 
malformations  occur  in  O.  Lamar ckiana.  I  mention 
them  briefly  because  I  have  not  laid  great  stress  on  ob- 


Other  Characters  in  Oenothera  Laniarckiaua.    489 

serving  them  minutely:  if  I  had,  this  hst  would  have 
been  considerably  longer. 

The  occurrence  of  buds  on  the  cotyledons  is  the  last 
example  of  one  of  these  commonly  recurring  anomalies 
that  I  shall  give.  The  young  plants  sometimes  come  up 
with  three  cotyledons  (p.  474),  sometimes  witli  two,  of 
which  one  is  more  or  less  deeply  split.  In  the  latter  case 
a  small  bud  is  sometimes  formed  in  the  fork  of  the  spht, 
which  looks  most  extraordinary,  especially  when  t'ne  un- 
split  part  of  the  cotyledon  is  fairly  large.  I  first  saw  this 
phenomenon  in  1 897 ;  since  then  I  have  seen  about  a 
dozen  examples  of  it  (Fig.  1 12).  Sometimes  I  succeeded 
in  growing  these  seedlings  to  maturity  and  in  getting  the 
adventitious  buds  to  develop;  they  behaved  like  ordinary 
rosettes,  and  it  was  sometimes  difficult  to  distinguish 
them  from  rosettes  duplicated  by  fasciation  (Fig.  108) 
without  separating  out  the  parts  in  question. 

Our  figure  113  shows  a  rosette  of  this  kind  in  July, 
i.  e.,  three  months  old  (1900).  The  cotyledon  was 
deeply  split  but  single  at  the  base.  The  base  of  the  ad- 
ventitious rosette  and  its  connection  with  the  cotyledons 
are  much  swollen ;  so  that  it  seems  to  come  very  close  to 
the  main  group  of  leaves,  but  as  a  matter  of  fact  it  is 
quite  sharply  separated  from  it. 

This  latent  capacity  to  produce  adventitious  buds 
seems  to  be  widely  distributed  in  my  cultures. 

The  facts  recorded  make  it  perfectly  evident  in  my 
opinion  that  the  potentialities  for  a  series  of  anomalies 
are  inherited  in  a  latent  condition  in  mv  Oenotheras. 


490  On  the  Latent  Capacity  for  Mutation, 


§  31.    THE  HYPOTHESIS  OF  A  PREMUTATION   PERIOD. 

The  mutations  of  Oenothera  Laniarckiana  which  have 
been  described  in  this  section  form  so  circumscribed  a 
group  of  phenomena  that  the  question  as  to  their  origin 
and  causes  can  hardly  be  avoided. 

There  can  be  no  doubt  that  I  have  neither  witnessed 
the  beginning  nor  the  end  of  these  mutations.  I  have 
evidently  only  been  able  to  follow  a  section  of  the  whole 
period  of  mutation.^ 

But  in  attempting  to  form  some  conception  as  to  the 
mode  of  origin  of  such  a  period  we  must  leave  the  sphere 
of  observation  for  that  of  hypothesis.  If  the  purpose 
of  doing  so  was  nothing  more  than  the  mere  elaboration 
of  the  theoretical  conceptions  I  should  drop  it  at  once. 
But,  as  a  matter  of  fact,  what  we  want  is  a  working 
hypothesis  which  may  result  in  bringing  the  origin  of 
such  a  period  within  the  range  of  experimental  inquiry. 

In  order  to  work  out  some  such  hypothesis  we  must 
look  to  the  facts  to  indicate  what  we  must  expect  to  find, 
that  is  what  we  really  have  to  investigate. 

We  came  to  the  conclusion  in  the  preceding  sec- 
tions that  a  mutation  is  not  the  result  of  the  sudden 
origin  of  a  new  character  but  of  the  manifestation  of  one 
already  present  in  a  latent  condition.  During  the  whole 
period  of  mutation  the  capacity  for  producing  dwarfs 
is,  apparently,  present  in  all  individuals.  So  is  that  for 
giving  rise  to  examples  of  lata.  On  the  other  hand  the 
capacity  for  producing  O.  brevisfylis  and  0.  laevifolia 
was,  presumably,  absent  during  the  whole  period  of  my 
experiments.      Moreover   a   number   of   possible,    or   at 

^  Which  is  still  lasting  (1908). 


The  Hypothesis  of  a  Premutation  Period.        491 

least  conceivable  mutations  did  not  appear — e.  g.,  white 
flowers. 

Our  conclusion  is  therefore  that  only  what  is  already 
present  in  a  latent  state  can  appear  during  the  period  of 
mutation;  but  nothing  or  almost  nothing  which  is  not 
already  there. 

Oenothera  Lamarckiana  would  appear  therefore  to 
be  laden  with  a  certain  number  of  latent  characters,  which 
it  splits  off  if  we  may  so  express  it,  from  time  to  time. 
Thus  it  may  perhaps  sometimes  *'split  off"  plants  which 
lack  one  or  more  such  latent  potentialities,  and  therefore 
be  no  longer  mutable  in  respect  of  these.  If  these  indi- 
viduals should  be  the  only  ones  which  ultimately  survive, 
the  mutation  period  would  be  at  an  end. 

When  and  how  did  the  latent  characters  arise?  Their 
origin  was  the  real  beginning  of  the  period  of  mutation, 
and  will  be  referred  to  in  future,  for  the  sake  of  brevity, 
as  premutation.  This  premutation  or  the  first  origin  of 
the  potentialities  of  the  later  mutations  is  evidently  an 
event  which  takes  place  in  a  latent  state.  It  may  be  ac- 
companied by  mutations;  though  that  does  not  seem  to 
be  essential.  It  can  of  course  only  be  made  known  to  us 
by  mutations ;  but  it  may  be  already  there  before  we  can 
perceive  any  trace  of  it. 

We  may  assume  that  all  potentialities  which  are  mani- 
fested during  a  period  of  mutation  arise  either  succes- 
sively or  at  once.  It  seems  possible  that  the  whole  group 
of  new  potentialities  might  arise  in  the  lifetime  of  a 
single  individual,  or  perhaps  in  the  brief  period  of  its 
sexual  life.  But  it  is  also  possible  that  several  genera- 
tions may  be  necessary  for  the  process. 

The  older  plant-breeders  thought  that  it  would  be 
possible  to  upset  the  internal  economy  of  a  plant  in  sucli 


492  On  the  Latent  Capacity  for  Mutation. 

a  way  as  to  make  it  highly  variable  or  mutable.  Louis 
ViLMORiN,  who  used  the  French  word  affoler  for  this 
operation,  proposed  the  following  method  :^  Look  through 
a  crop  for  individuals  which  differ  most  from  the  normal 
in  any  direction,  not  necessarily  the  one  leading  to  the 
ideal  aimed  at.  Sow  its  seeds;  and  in  the  crop  raised, 
do  not,  as  in  ordinary  selection,  choose  the  individuals 
which  deviate  most  in  the  same  direction,  but  such  as  are 
abnormal  in  the  opposite  one.  Repeat  this  mode  of  se- 
lection through  a  series  of  generations  and  it  is  antici- 
pated, says  ViLMORiN,  that  the  variability  will  gradually 
increase,  until  finally  it  becomes  so  great  that  it  will 
give  rise  to  any  new  character  desired. 

It  does  not  appear  that  Vilmorin  carried  out  such  an 
experiment  and  still  less  that  he  ever  saw  the  result  he 
anticipated. 

Nevertheless  his  suggestion  deserves  attention ;  it  may 
contain  the  germ  of  truth.  And  anyhow  the  method 
would  be  likely  to  lead  to  the  discovery  of  latent  muta- 
tions. 

One  of  the  most  important  conclusions  which  may 
be  drawn  from  these  general  considerations  is  that  a 
premutation  must  be  due  partly  to  internal  and  partly 
to  external  causes.  The  former  determine  what  shall 
arise ;  the  latter  when  it  arises. 

The  external  causes  must  be  other  than  the  ordinary 
conditions  of  life  under  which  the  species  remain  con- 
stant. On  the  other  hand  they  must  be  such  as  appear 
not  too  rarely  in  the  natural  state.  I  assume  these  causes 
to  be  perhaps  a  combination  of  extremely  favorable  with 
extremely  unfavorable  influences :  this  view  would  at  any 

_^  Louis  Vilmorin,  Notice  sur  ramcUoration  des  plantes  par  le 
semis.     Nouv.  Edition,  1886,  p.  36. 


The  Hypothesis  of  a  Premutation  Period.        493 

rate  account  for  the  comparative  rarity  of  their  appear- 
ance. 

We  should  therefore  have  to  determine,  experimen- 
tally, the  effect  of  the  combination  of  such  extremes.  I 
do  not  regard  this  as  in  any  way  impossible.  For  ex- 
ample, take  very  weak  buds  and  their  shoots,  or  very 
weak  flowers  and  supply  them  with  as  much  nutriment 
as  possible.  Just  as  saplings  or  the  strong  shoots  pro- 
duced by  resting  buds,  often  develop  hitherto  latent  char- 
acters (such,  e.  g.,  as  the  well-known  intemiediate  forms 
between  leaves  and  thorns  in  the  common  barberry)  ;  so 
perhaps  they  might  also  be  induced  to  give  rise  to  muta- 
tions. A  very  rapid  multiplication  is  generally  regarded 
as  an  effective  inducement  to  the  production  of  muta- 
tions ;  the  reason  for  this  being  probably  that  the  seeds 
which  would  otherwise  perish  at  or  immediately  after 
germination  find  the  necessary  conditions  for  full  growth. 
The  seeds  in  question  are  those  which  have  suffered  from 
unfavorable  circumstances ;  and  this  gives  us  the  contrast 
we  spoke  of  above.  For  the  sake  of  experiment,  there- 
fore, we  should  collect  the  seed  from  the  small,  late, 
lateral  twigs  of  the  higher  orders,  and  sow  it  with  all 
possible  care.^ 

Let  us  now  suppose  that  a  genuine  premutation  period 
has  been  induced  or  at  any  rate  discovered.  \\'hat  must 
be  expected?  In  other  words  let  us  suppose  that  the 
potentialities  for  a  whole  series  of  mutations  have  arisen 
in  a  plant  or  a  group  of  plants.  Will  each  potentiality 
actually  give  rise  to  a  mutation,  and,  hence,  to  a  new 
species  (fit  or  unfit)  ?  Chance  will  obviously  have  a  great 
deal  to  do  with  it.     The  latent  characters  are  evidently 

^  Experiments  of  this  kind  would  obviously  have  to  he  continued 
through  some  years;  the  greatest  difficulty  is  the  choice  of  suitable 
plants. 


494  On  the  Latent  Capacity  for  Mutation. 

not  affected  by  the  struggle  for  existence  in  which  the 
organisms  bearing  them  are  engaged ;  they  do  not  weigh 
in  the  scale  on  the  one  side  or  on  the  other.  They  multiply 
or  perish  precisely  as  their  bearers  do.  But  one  Oenothera- 
f  ruit  may  bear  between  one  and  two  hundred  seeds ;  and  a 
vigorous  plant  bears  hundreds  of  fruits.  So  that  it  prac- 
tically never  happens  that  all  the  seeds  produced  become 
flowering  plants.  It  is  very  largely  a  matter  of  chance 
which  of  these  survive,  and  therefore  a  matter  of  chance 
which  latent  mutations  continue  and  which  perish. 

I  conclude  from  this  that  the  number  of  mutations 
actually  observed  is  no  measure  at  all  of  the  number 
which  presumably  arose  during  the  premutational  period. 

We  must  think  of  the  origin  of  groups  of  closely  re- 
lated species  in  other  genera  and  families  as  essentially 
analogous  to  the  mutational  period  in  Oenothera  La- 
mar ckiana.  Examples  of  such  groups  are  the  long  se- 
ries of  elementary  species,  our  knowledge  of  which  we 
owe  to  Jordan  and  his  pupils ;  and  the  well-known  nebu- 
lous groups  of  the  old  systematists  such  as  Fries,  Nageli 
and  others.  It  is  reasonable  to  suppose  that  the  numer- 
ous elementary  species  of  Draba  verna  all  arose  in  a 
single  period  in  a  small  locality  and  that  they  have  spread 
thence,  hither  and  thither  over  the  whole  of  Europe.^ 
Or  perhaps  they  have  arisen  during  the  period  of  distribu- 
tion. The  same  may  be  said  of  Viola  tricolor,  Helian- 
themitm  vulgare,  etc.  The  whole  appearance  of  Draba 
verna,  at  present, points  to  a  period  of  mutation  of  exactly 
the  same  kind  as  that  of  Oenothera  Lamarckiana. 

^  A  few  species  of  Draba  verna  ought  to  be  cultivated  side  by 
side  in  every  botanical  garden.  Their  differences  and  constancy  are 
perfectly  obvious  and  such  as  to  strike  the  eye  of  every  visitor.  I 
have  only  two  species  in  cultivation;  but  even  those  have  been  of 
general  interest  already. 


The  Hypothesis  of  a  Premutation  Period.        495 

The  genera  Rosa,  Rubus,  Hieraciiim,  Salix  and  some 
other  types  rich  in  species  formed  the  nebulous  groui)s 
of  the  older  systematists :  they  were  extremely  rich  in 
forms  that  could  hardly  be  distinguished.  Without  cul- 
tivation we  can  only  have  a  provisional  knowledge  of 
their  species  and  the  cultivation  of  some  of  these  forms 
through  even  a  few  generations  would  be  no  light  task. 
But  the  richness  of  forms  (exclusive  of  hybrids),  is 
comparable  to  that  of  Draba  verna  and  Oenothera  La- 
marckiana,  and  clearly  points  to  the  existence  of  muta- 
tion periods,  belonging  partly  to  the  past  and  partly  per- 
haps to  the  present. 

The  most  conclusive  point  of  all  is  however  the  ne- 
cessity of  assuming  such  a  period  to  have  occurred  in  the 
group  of  Oenothera  biennis  (the  subgenus  Onagra), 
which  is  absolutely  analogous  to  the  Laniarckiana-group 
(see  p.  440). 

Finally,  a  few  words  must  be  devoted  to  the  ques- 
tion as  to  when  the  premutation  period  occurred  in  our 
particular  case  of  the  Oenothera  Lamarekiana  at  Hilver- 
sum.  Two  possibilities  present  themselves.  Either  the 
plant  was  already  in  a  period  of  mutation  when  its  seeds 
were  first  sown  there  by  Mr.  Six  (in  about  1870,  see  p. 
266).  Or  the  period  began  on  the  spot.  In  the  former 
case  the  Oenothera  must  have  already  been  mutable  and 
this  property  had  simply  escaped  observation.  This 
seems  hardly  likely  because  O.  nanella,  0.  gigas  and  O. 
laevifolia,  if  they  had  come  under  the  eyes  of  nursery- 
men or  amateurs,  would  certainly  have  been  thought 
worth  cultivation,  and  would  have  been  put  on  the  market. 
But  no  'Varieties"  of  0.  Lamarekiana  occur  either  in 
descriptive  works,  or  in  catalogues. 

In  the  latter  case;  we  should  suppose  that  the  rapid 


496  On  the  Latent  Capacity  for  Mutation. 

multiplication  of  our  Oenotheras  between  the  years  1870 
and  1886  (p.  266)  was  the  cause  of  the  appearance  of 
the  premutation  period  and  therefore  the  beginning  of 
mutability  in  this  case.  And  this  supposition  agrees  so 
well  with  the  little  that  we  know  about  the  origin  of  spe- 
cies in  general  that  it  deserves  attention,  to  say  at  least, 
until  definitely  disproved.^ 

We  may  sum  up  the  *¥oregoing  in  the  generalization 
that  each  jnutational  period  is  initiated  by  a  premutational 
one,  in  which  the  new  characters,  which  are  to  appear, 
arise  in  a  latent  condition  under  the  influence  of  external 
causes. 

^Afterwards  I  found  that  seeds  of  Oenothera  Lamarckiana  from 
other  sources,  especially  from  the  strains  of  different  nurseries,  may 
produce  the  same  mutations.  From  this  I  conclude  that  the  period 
of  mutation  must  be  older  than  the  occurrence  in  the  field  at  Hilver- 
sum,  and  probably  as  old  as  the  introduction  of  the  present  strains 
into  European  gardens,  which  was  effected  by  Messrs.  Carter  & 
Sons  about  i860  from  seed,  gathered  in  Texas.  (See  Berichte  der 
deutschen  Bot.  Gesellschaft,  1905,  Bd.  XXIII,  p.  382. — Note  of  1908.) 


V.    CONCLUSION. 

Perhaps  the  most  important  general  result  of  my  ob- 
servations on  the  origin  of  species  in  the  genus  Oenothera 
is  the  proof  which  they  afford  that  this  phenomenon  can 
be  dealt  with  experimentally.  Hitherto  the  general  opin- 
ion has  been  that  this  extraordinarily  important  phenom- 
enon was  amenable  neither  to  direct  investigation  nor 
even  to  direct  observation.  The  experience  of  horti- 
culture is  sufficient  to  demonstrate  the  fact  that  new 
forms  do  sometimes  appear  and  less  rarely  perhaps,  than 
is  imagined.  But  when  they  appear  it  is  too  late  to  at- 
tempt to  discover  how  they  arose.  We  may  try  to  explain 
how  this  happened,  but  it  is  no  longer  possible  to  deal 
with  the  question  experimentally. 

For  this  object  it  is  necessary  to  have  a  plant  which 
happens  to  be  in  a  mutation  period,  i.  e.,  which  has  the 
power  of  giving  rise  repeatedly  to  new  species.  Such 
plants  had  hitherto  not  been  found. 

The  way  to  look  for  mutable  plants  is  to  make  very 
extensive  sowings  of  various  species.  Seeds  are  collected 
either  from  wild  plants  or  from  plants  that  have  run  wild 
or  lastly  from  cultivated  plants  which  one  has  oneself 
grown  for  a  sufficient  length  of  time  to  make  certain 
that  they  are  free  from  the  effect  of  any  previous  cross- 
ings that  may  have  taken  place.  I  have  either  collected 
the  seeds  in  the  field,  or  transplanted  a  few  plants  into 


498  Conclusion. 

the  garden  and  allowed  them  to  bear  fruit  in  a  state  of 
perfect  isolation.  We  can  be  guided,  to  a  certain  extent, 
in  our  choice  of  species  by  observations  in  the  field ;  either 
by  finding  new  varieties  or  subspecies;  or  by  a  certain 
richness  in  partial  variations,  or  by  so-called  monstrosi- 
ties. The  latter  are  due  to  latent  potentialities  which  are 
manifested  from  time  to  time  on  isolated  twigs,  leaves, 
etc.  It  is  natural  to  conclude  that  where  such  latent 
potentialities  occur  in  unusually  large  numbers,  others 
may  be  expected  and,  amongst  them,  those  that  we  are 
looking  for. 

I  have  conducted  a  considerable  number  of  such  ex- 
periments, both  before  and  after  I  began  my  main  ex- 
periment, particularly  with  species  of  our  indigenous 
flora,  on  such  a  scale  as  the  amount  of  seed  harvested 
would  allow.  For  example,  I  sowed  seeds  of  Capsella 
Bursa  Pastoris,  Sisynibriuin  Alliaria,  Daunts  Carota, 
Cvnoglossuni  officinale,  Verhasciun  thapsifornie,  Aster 
Tripolium,  Bid  ens  cernua,  Thrincia  hirta,  Crcpis  biennis, 
Ccntaurca  nigra  and  a  whole  series  of  other  wild  species. 
They  were  mostly  forms  which  attracted  my  attention 
by  the  possession  of  fasciations,  concrescences,  or  other 
kinds  of  abnormality.  I  cultivated  the  monstrosities  for 
longer  or  shorter  periods  of  years  in  order  to  test  their 
hereditary  nature. 

Almost  all  the  species  proved  themselves  to  be  im- 
mutable.^ I  conclude  from  this  that  most  of  the  wild 
species  in  our  neighborhood  happen  to  be  in  an  immutable 
state.  In  other  places  the  same  species  may  of  course 
be  mutable,^  for,  according  to  the  theory,  mutability  is 

^  See  also  the  first  part  of  the  second  volume. 

^This  seems  to  be  true  of  Capsella  Bursa  Pastoris,  near  Landau; 
see  SoLMS  Laubach^  Bot.  Zeitung,  1900,  October  part. 


Conclusion.  499 

not  an  intrinsic  character  of  a  particular  species,  but  a 
passing  phase  in  which  the  plants  in  a  particular  locality 
may  happen  to  be. 

Only  one  species  answered  my  purposes:  Oenothera 
Lamar ckiana.  Even  on  the  spot  where  I  found  it,  it  gave 
promise  of  a  more  favorable  result  than  all  the  rest.  In 
the  first  place,  it  was  not  a  genuine  wild  form,  but  an 
escaped  one,  which  had  spread  from  a  bed  to  a  deserted 
field  close  by,  where  it  had  multiplied  abundantly.  A 
rapid  multiplication  of  this  kind  is  one  of  the  supposed 
causes  of  mutability.  In  the  second  place  it  was  very 
rich  in  partial  abnormalities ;  not  only  in  the  common 
ones  like  floral  anomalies,  pitcher  formations,  fascia- 
tions,  connations,  adnations,  etc.,  but  in  the  rarer  ones, 
like  the  development  of  secondary  axil  buds  in  the  in- 
florescence and  so  on.  In  the  third  place  I  found  iso- 
lated delicate  plants  with  narrow  leaves  which  only 
formed  rosettes  and  then  died.  I  was  unable  to  studv 
them  further  at  the  time  but  they  have  since  turned  o\\\ 
to  be  a  perfectly  good  new  species  (0.  elliptica).  And 
lastly  I  found  there  two  well  characterized  forms  which 
were  hitherto  unknown  and  have  since  proved  to  be  con- 
stant (O.  lacvifolia  and  O.  hrevistylis) . 

But  the  result  of  sowing  the  seed  collected  in  the 
field,  was  decisive.  I  did  this  first  in  1887  and  repeatedly 
afterwards,  but  particularly  in  1889.  IMy  very  first  cul- 
ture gave  me  what  I  wanted ;  it  contained  a  form,  which 
differed  sharply  from  the  normal  in  almost  every  feature, 
which  had  not  been  seen  in  the  field  before  and  was  other- 
wise also  absolutely  unknown.  This  was  the  Oenothera 
lata.  In  the  following  year  I  sowed  the  seeds  of  plants 
which  I  had  brought  with  me  from  Hilversum  in  the 
autumn  of  1886  as  rosettes:  they  gave  me  the  same  form 


500  Conclusion. 

0.  lata  and  another  besides,  0.  nanella',  both  were  repre- 
sented by  several  examples  (p.  224).  I  sowed  seeds, 
collected  in  the  field,  again  in  1889  on  a  larger  scale  and 
again  got  the  same  two  forms,  and  yet  a  third  form, 
hitherto  unknown,  O.  rubrmervis  (p.  304).  Later  on  I 
found  the  two  former  (0.  lata  and  0.  nanella)  in  the 
field  as  well  (1894). 

This  rapid  succession  of  discoveries  decided  me  to 
practically  give  up  the  experimental  sowings  of  the  other 
species  and  to  investigate  Oenothera  Lamarckiana  as 
minutely  as  possible.  Two  methods  of  investigation  pre- 
sented themselves.  On  the  one  hand,  observation  in  the 
field,  together  with  a  yearly  sowing  of  seeds  collected 
there.  On  the  other,  the  cultivation  in  the  garden  of 
families  of  plants  through  many  generations.  I  adopted 
the  latter  without  however  neglecting  the  former.  And 
in  this  connection  I  wish  to  particularly  emphasize  the 
point  that  my  cultures  are  nothing  more  than  a  repe- 
tition of  what  occurs  in  nature.  My  idea  was  merely 
to  follow  the  natural  process  of  the  origin  of  new  species 
as  accurately  as  I  could,  by  excluding,  wherever  necessary, 
the  sources  of  error  and  uncertainty  which  are  the  un- 
avoidable result  of  free  fertilization  by  insects. 

I  have  made  observations  in  the  field  every  year  since 
1886;  I  thus  witnessed  the  origin  of  new  forms,  the 
majority  of  which,  however,  perished.  They  were  es- 
sentially the  same  as  those  in  my  cultures.  There  is  no 
reason  for  supposing  that  any  forms  arose,  in  my  garden, 
which  would  not  also  have  arisen  in  nature  under  suffi- 
ciently favorable  circumstances.  In  nature  there  is  not 
room  enough  for  all  seeds  to  germinate,  still  less  to  give 
rise  to  adult  plants:  so  that  the  rarer  and  weaker  sorts 
perish;  whereas  in  my  garden  they  are  transplanted  and 


Conclusion.  501 

carefully  tended.  It  is  this  fact,  together  with  the  ex- 
clusion of  the  visits  of  insects,  which  are  the  main  ad- 
vantages of  the  method  of  cultivation. 

The  experiment  does  not  create  anything  new.  It 
merely  enables  us  to  see  and  study  what  happens  in 
nature. 

H:  ^  4: 

A  glance  at  my  cultures  shows  the  mutation  period 
which  I  have  studied  to  be  a  definite  whole.  It  com- 
prises a  sharply  circumscribed  group  of  phenomena, 
narrowly  delimited  in  every  respect.  I  mean,  the  same 
events  repeat  themselves  regularly;  new  ones  occur  but 
seldom,  and  when  they  do,  they  conform  to  rules  already 
ascertained.  We  do  not  see  a  hopeless  chaos  of  forms 
which  merge  into  one  another;  nor  is  the  variability  an 
unlimited  one.  On  the  contrary  we  see  a  relatively  small 
number  of  perfectly  distinct  and  constant  forms  which 
we  find  appearing  again  and  again. 

There  can  be  little  question  that  I  have  witnessed 
neither  the  beginning  nor  the  end  of  the  period.  Every- 
thing points  to  the  conclusion  that  it  was  in  full  swing 
in  the  locality  when  I  first  visited  it,  and  that  the  poten- 
tiality for  everything  which  appeared  later  was  already 
present  there  at  that  time.  I  did  not  see  the  majority  of 
the  forms  during  the  first  few  years  probably  only  be- 
cause I  was  not  on  the  look-out  for  them.  F(^r  when 
once  I  had  got  to  know  a  form  I  found  it  every  year 
afterwards,  with  very  few  exceptions. 

It  is  highly  improbable  that  I  have  exhausted  the 
whole  wealth  of  latent  potentialities  in  OcnotJicra.  On 
the  contrary  it  is  possible  that  even  tlie  most  beautiful 
and  important  mutations  and  those  deviating  most  from 


502  Conclusion. 

the  type  have,  so  far,  escaped  me  altogether.  I  have 
hitherto  only  experimented  with  ordinary  sowings ;  and 
my  object  has  been  rather  to  become  familiar  with  the 
principles  of  mutation,  than  to  bring  to  light  a  multitude 
of  novelties. 

I  gradually  came  to  see  that  the  method  of  searching 
for  mutations  was  capable  of  improvement  in  many  re- 
spects. There  seem  to  be  two  main  ways  of  doing  this : 
the  choice  of  seeds  and  hybridization.  If  the  harvest 
turns  out  to  be  meagre  for  one  reason  or  another,  or  the 
fertility  of  the  seeds  diminishes  greatly  (that  is  to  say 
only  a  small  percentage  remain  fertile)  the  prospect  of 
getting  mutations  in  general,  or  at  any  rate  of  getting 
particular  forms,  seems  to  be  considerably  increased. 
For  example  in  a  sample  of  seeds  which  had  been  kept 
for  5%  years  the  fertility  went  down  from  70  to  5  seeds 
per  cubic  centimeter;  but  the  percentage  of  mutations 
went  up  from  1-5%  to  40%  (p.  263).  In  another  cul- 
ture only  about  30  seeds  germinated  out  of  the  whole 
harvest  sown;  but  of  these,  12  gave  rise  to  mutants  which 
formed  therefore  40%  of  the  population.  And  the  view 
that  crossing  increases  variability  is  generally  held  and 
seems  to  be  supported  by  some  of  my  experiments. 

My  cultures  were  conducted  on  the  following  lines. 
From  seeds  or  plants  which  I  gathered  at  Hilversum  I 
derived  my  so-called  families  as  follows :  Seeds  were 
collected  every  year  from  a  few  (e.  g.,  4-10)  individuals. 
These  were  chosen  as  being  typical  examples  of  the  fam- 
ilies in  question  and  were  either  left  to  be  fertilized  by 
insects  on  some  isolated  spot  (1887-1894),  or  (as  in 
later  years)  were  protected  from  the  visits  of  insects  by 
parchment  bags  and  artificially  fertilized  with  their  own 
pollen.     It  was  only  in  /a/a-families  that  crossing  always 


Conclusion.  503 

took  place  (this  species  being  exclusively  female),  the 
pollen  of  O.  Lamarckiana  being  generally  used  for  the 
purpose. 

Thus  each  family  has  a  single  and  pure  main  stock. 
Branches  of  it  are  to  be  regarded  as  separate  families. 
The  mutations  arose  from  these  main  stocks. 

The  great  advantage  of  this  method  is  tliat  it  enables 
us  to  knov^  the  ancestors  of  each  mutation  through  one 
or  more  generations.  And  this  is  just  what  is  lacking 
in  observations  made  in  the  field,  and  in  horticultural 
data.  The  number  of  generations  known  is  great  in 
direct  proportion  as  the  date  of  the  mutation  in  question 
is  recent.  The  pedigree  of  every  single  mutation  can  be 
determined  in  my  records,  and  found  to  be,  for  exami)le, 
a  pure  line  of  Lamarckiana,  or  laevifolia  or  riihrincrvis 
or  lata,  and  so  forth,  according  to  the  family.^  One 
would  like  to  complete  the  series  of  ancestors  for  the 
period  of  time  previous  to  the  year  1886,  in  which  I 
first  collected  seeds  and  plants.  I  have  no  direct  obser- 
vations wdiich  will  help  us ;  but  it  is  known  that  the  plant 
began  to  spread  over  the  field  about  1870.  It  is  highly 
probable  that  new  forms,  if  they  had  flowered  during 
these  years,  would  have  been  found  flowering  afterwards 
in  the  field  also,  after  the  rapid  multiplication  which  had 
taken  place.  We  may  therefore  consider  ourselves  justi- 
fied in  mentally  carrying  back  the  pure  unbroken  line  to 
1870. 

The  individual  mutations  in  the  various  families  arise 

wholly  independently  of  one  another ;  that  is  to  say  each 

one  arises  directly  from  the  main  stem.     If  we  harvest 

the  seed  of  mutants,  or  fertilize  other  plants  with  their 

*The  pedigrees  for  the  3  chief  families  can  be  found  on  the  fol- 
lowing pages:  Lamarckiana-i^mWy,  pp.  224  and  262;  lacvitoha-iiww- 
ily,  p.  2"/ 2,',  /a/a-family,  pp.  285  and  288. 


504  Conclusion. 

pollen,  new  lateral  branches  arise  from  the  family ;  the 
members  of  such  lateral  branches  are  not  henceforth 
called  mutants.  The  independence  is,  however,  only  ex- 
ternal, the  analogous  mutants  being  related  to  one  an- 
other as  sisters,  or  as  nieces  and  aunts,  etc.  The  identity 
of  their  features  is  obviously  due  to  the  fact  that  they 
originate  from  the  same  latent  potentialities  in  the  main 
stem. 

But  each  mutation  arises  suddenly  and  directly  from 
the  main  stem  without  any  preparation  and  with  all  its 
characters.^  Every  new  dwarf  that  appears  is  as  small 
as  the  dwarfs  of  the  fourth  and  fifth  and  later  genera- 
tions. Each  /a/a-mutant  is  as  purely  female  as  the  lata 
of  the  present  day  which  has  been  cultivated  for  ten 
generations.  The  various  riibrinerzns-plsinis  which  I  have 
cultivated  during  the  course  of  many  years  for  various 
purposes  are  indistinguishable  from  the  newly  arisen 
mutants  of  these  forms.  0.  gigas  only  arose  three 
times,  O.  scintillans  fourteen  times.  But  each  time  they 
appeared  with  exactly  the  same  characters. 

The  occurrence  of  transitional  and  intermediate  forms 
is  a  very  important  point.  These  do  certainly  occur; 
but  they  are  phenomena  of  individual  variability  and  not 
of  mutability.  For,  in  the  first  place,  these  transitions 
do  not  appear  before  the  new  species,  but,  at  most,  simul- 
taneously with  it;  usually,  however,  not  till  well  after  it 
has  arisen.  These  transitions  are  not  therefore  the  steps 
which  must  be  traced  by  a  new  form  in  its  origination; 
this  origin,  far  from  being  reached  by  these  steps,  is  ab- 
solutely independent  of  them.     The  intermediate  forms 

^  These  characters  are  therefore  to  be  regarded  for  each  muta- 
tion as  expressions  of  one  single  internal  change.  See  §  13.  pp.  327- 
330.  For  the  relative  frequency  of  the  appearance  of  the  various 
mutations,  the  so-called  mutation-coefficients,  see  §   14,  p.  337. 


Conclusion.  505 

are  not  in  fact  what  they  are  called,  in  the  strict  sense 
of  the  term ;  they  are  only  more  or  less  incomplete  copies 
of  a  type  already  existing.  They  may  be  observed  just 
as  well  in  the  later  as  in  the  earlier  generations :  in  fact 
better,  because  there  is  little  prospect  of  finding  them  at 
first,  the  number  of  mutants  being  so  small.  It  is  onlv 
when  the  latter  can  be  propagated  by  an  unlimited  quan- 
tity of  seed  that  complete  series  of  transitional  forms  may 
be  expected. 

These  transitions  are  partly  atavistic  phenomena, 
partly  instances  of  ordinary  variability ;  and  partly  of 
transgressive  variability.  An  instance  of  atavism  is  af- 
forded by  0.  nanella  which  may  be  characterized  for  the 
whole  of  its  life  by  unstalked  leaves,  but  which  during 
a  brief  period  of  its  youth  exhibits  the  stalked  leaves  of 
its  ancestors  (see  Fig.  78  on  p.  362).  This  case  is  per- 
fectly analogous  to  the  well-known  embryonic  forms  of 
many  other  plants.  Atavism  is,  so  to  speak,  accidentally 
brought  about  in  0.  laevifolia  whose  leaves,  normally 
smooth,  are  sometimes  crumpled,  either  singly  or  over 
the  whole  plant  when  it  is  an  unhealthy  one.  Most  char- 
acters exhibit  transgressive  variability  more  or  less ;  but 
there  is  always  a  wide  gap  between  the  largest  0.  nancUa 
and  the  smallest  flowering  O.  Lamarckiana.  The  leaves 
of  O.  gigas  exhibit  a  high  degree  of  transgressive  varia- 
bility; they  may  be  broader  and  narrower  than  those  of 
the  parent  species  and  sometimes,  even,  come  to  re- 
semble those  of  ruhrinervis  and  other  narrow  leaved 
forms.  Further,  the  size  of  the  flowers  varies  directly 
with  the  vigor  of  the  plants,  in  all  the  species. 

If  we  deal  with  one  character  at  a  time  we  can  make 
perfectly  continuous  series  embracing  O.  Lainarckiaua 
and  all  the  species  which  have  arisen  from  it.     Vor  ex- 


506  Conclusion. 

ample  for  the  breadth  of  the  leaves,  the  length  of  the 
fruits,  the  size  of  the  flowers,  etc.  But  exactly  the  same 
can  be  done  for  those  forms  which  have  been  recognized 
as  species  by  the  best  systematists  and  exhibit  such  ex- 
cellent points  of  difference  as,  for  example,  the  size  of 
the  flowers  in  Oenothera  biennis  L.  and  0.  ninricata  L. 

The  boundaries  between  my  new  species  are  no  more 
obliterated  by  transgressive  variability  than  are  those 
between  recognized  types.  The  phenomenon  is  a  very 
general  one  in  the  whole  animal  and  vegetable  kingdom ; 
and  is  very  apt  to  land  any  one  who  confines  his  attention 
to  one  character  at  a  time,  into  difficulties.  In  settling  the 
identity  of  a  doubtful  case  situated  in  the  borderland  be- 
tween two  types  the  other  characters  of  the  doubtful  in- 
dividual must  receive  attention ;  for,  in  spite  of  the  phe- 
nomenon of  correlation,  the  other  characters  will  almost 
always  show  to  which  side  the  doubtful  form  really,  be- 
longs. And  if  this  comparison  does  not  suflice,  we  must 
resort  to  experimental  sowings ;  the  direction  in  which 
the  offspring  regress  will  leave  no  doubt  as  to  the  specific 
type  to  which  the  doubtful  individual  belonged. 

In  this  respect  as  in  all  others,  my  new  forms  of 
Oenothera  are  species  and  not  varieties ;  with  the  single 
exception  of  O.  nanella  (see  §  18,  pp.  360-363).^  The 
difference  between  a  species  and  a  variety  is  that  whilst 
a  variety  is  marked  by  the  possession  of  a  single  distinc- 
tive character  a  species  or  subspecies  differs  from  its 
nearest  allies  in  almost  all  its  parts.  Lack  of  pigment,  hairs 
or  spines ;  branching  of  leaves  or  stems ;  or  an  abnormal 
development  of  these  characters;  laciniate  leaves  and 
petals,  etc. — such  are  the  characters  of  true  varieties. 
There  are  two  further  points  about  varieties.     First  the 

*  On  this  point  see,  especially,  the  second  volume. 


Conclusion.  507 

whole  ''habit"  of  the  plant,  in  so  far  as  it  is  not  directly 
modified  by  the  varietal  character,  remains  unaltered ; 
color  varieties  can  only  be  recognized  by  their  colcjr; 
thornless  ones  only  by  the  absence  of  thorns ;  and  so 
forth.  True  species  are  on  the  other  hand  distinguishable 
from  one  another  in  almost  every  organ  and  at  almost  any 
age.  Secondly,  the  character  of  a  variety  usually  does 
not  exhibit  transgressions.  White  flowered  varieties,  al- 
though they  often  have  a  bluish  or  reddish  blush  in  their 
petals,  are  almost  always  paler  than  the  palest  variants  of 
their  parent  species.  The  very  reverse  is  the  case  with 
specific  characters  of  which  the  extreme  variants  may  not 
only  meet  but  often  overlap. 

New  species  differ  from  varieties  in  yet  another  way. 
The  latter  usually  occur  in  several  genera  and  families 
under  exactly  similar  forms,  which  are  as  a  rule,  given 
the  same  or  synonymous  names.  But  I  have  sought  in 
vain  for  forms  analogous  to  my  new  species  with  the 
single  exception  of  the  dwarfs.  Perhaps  also,  0.  lacri- 
folia  which  is  distinguished  by  the  absence  of  crumples 
in  its  leaves,  and  O.  hrevistylis  with  its  partial  loss  of  the 
inferior  ovary  should  be  regarded  as  true  varieties ;  they 
are  just  the  two  forms  which  have  never  arisen  in  my 
cultures.  But  apart  from  these,  the  new  species  are  with- 
out parallel  either  in  the  genus  Oenothera  or  elsewhere 
in  the  vegetable  kingdom. 

If  we  regard  varieties  as  having  arisen  by  the  loss  (or 
latency)  of  an  old  character,  it  seems  reasonable  to  re- 
gard species  as  having  arisen  by  the  origin  of  a  new  one. 

The  question  as  to  the  constancy  of  the  now  forms  is 
one  of  the  greatest  importance.  And  it  may  be  stated 
straight  away  that  the  character  is  not  one  which  is  at- 
tained by  repeated  selection.     The  view  that  at  least  a 


508  Conclusion. 

great  many  subspecies  and  varieties  are  not,  or  at  any 
rate  not  yet,  constant  and  that  they  revert  to  the  parent 
species  from  time  to  time  is  commonly  held.  It  is  this 
that  is  meant  by  the  statement  that  varieties  are  incipient 
species.     This  conception  is  however  entirely  erroneous. 

My  new  species  are  either  absolutely  constant  from 
the  beginning,  without  the  slightest  trace  of  reversion; 
or,  when  they  are  not,  exhibit  no  increase  in  constancy, 
in  response  to  selection. 

In  order  to  test  the  constancy  of  the  new  forms  di- 
rectly after  their  arising  from  O.  Lamarckiana  or  other 
families  one  has  to  artificially  fertilize  the  mutants  them- 
selves with  their  own  pollen.  Large  quantities  of  the  seed 
are  then  sown ;  and  as  the  new  species  is  easily  and  cer- 
taii^ly  recognized  during  the  first  months  of  its  life,  be- 
fore it  develops  a  stem,  some  hundreds  or  even  thousands 
of  seedlings  can  be  recorded.  Of  these  only  as  many  as 
can  be  conveniently  accomodated  are  chosen,  at  random ; 
and  cultivated  until  they  flower  and  ripen  their  fruits. 
The  constancy  of  a  new  form  can  be  determined  by  grow- 
ing it  in  this  way  for  a  number  of  generations.  From 
the  very  beginning  O.  gigas,  O.  ruhrinervis ,  O.  oblonga, 
O.  alhida,  O.  Icptocarpa,  O.  semilata  and  O.  nanella  were 
absolutely  constant. 

O.  schitillans,  0.  clliptica  and  0.  sitblinearis,  on  the 
other  hand,  proved  to  be  inconstant.  Only  a  small  pro- 
portion of  the  seeds  of  these  forms  repeat  the  parental 
type.  The  others  revert  to  O.  Lamarckiana  or  produce 
other  mutations.  0.  scintillans  usually  did  not  repeat  it- 
self in  more  than  30%  of  its  offspring  and  could  not  be 
got  to  increase  the  proportion  by  continued  selection ;  the 
others  did  not  furnish  sufficient  seeds  for  conclusive  ex- 
periments. 


Conclusion.  509 

Inconstant  species^  do  not  seem  to  occur  in  nature. 
And  if  they  did,  they  would  be  bound  to  disappear  sooner 
or  later  because  the  atavists,  which  they  produce  every 
year,  would  probably  be  constant,  and  soon  supplant  the 
inconstant  form. 

We  see  therefore  that  in  the  process  of  the  origin  of 
new  species  some  certainly  do  arise  which  are  not  capable 
of  existence  for  any  length  of  time.  Nature  does  not 
confine  herself  to  producing  just  what  is  wanted;  her 
creative  power  seems  to  be  almost  unlimited.  She  fur- 
nishes every  possibility,  so  to  speak,  and  leaves  it  to  the 
environment  to  choose  what  suits  it.  In  other  words 
mutability  is  indiscriminate. 

Could  the  new  species  maintain  themselves  in  nature  ? 
This  is  a  question  which  naturally  presents  itself.  I  have 
conducted  no  experiments  in  this  direction.  But  it  is  a 
fact  that  0.  laevifolia  and  0.  brevistylis  have  survived  the 
struggle  for  existence  at  Hilversum  for  a  long  period  of 
time.^  In  my  garden  the  plants  certainly  appear  to  be 
less  resistent  than  they  would  be  in  nature,  partly  on 
account  of  the  amovtnt  of  manure  they  get,  partly  because 
there  is  no  selection  which  kills  off  the  delicate  ones  in 
early  youth,  and  partly  and  in  fact  chiefly,  on  account  of 
my  preference  for  annuals.  For  example  annual  ohlonga 
set  far  too  little  seed ;  biennial  ones  give  a  good  harvest. 
O.  rubrinervis  as  an  annual  is  very  brittle,  as  a  biennial 
very  strong;  and  so  forth.  Both  these  and  O.  gigas 
would  maintain  themselves  Avell  in  nature  if  they  grew 
in  the  biennial  form;  and  would  perhaps  form  just  as 
good  species  as  the  forms  imported  from  America,   O. 

*For  the  justification  for  this  expression  see  §  19,  PP-  377-379- 

^They  are  still   seen  to  be  growing  in  the  field  at   Hilversum 
(Note  of  1908.) 


510  Conclusion. 

biennis  and  0.  mnricata.  0.  alhida  would  certainly  be 
too  weak;  and  the  inconstant  and  sterile  or  partly  sterile 
forms  would  obviously  perish  sooner  or  later. 

But  direct  investigation  is  necessary  before  a  satis- 
factory answer  to  this  question  can  be  given. 

Lastly,  let  us  examine  my  results  from  a  theoretical 
standpoint.  Two  points  stand  out  prominently.  First, 
the  question  as  to  the  origin  of  the  whole  mutation  pe- 
riod ;  and  secondly  the  analogy  between  the  phenomena 
observed  and  the  origin  of  species  in  general. 

We  regard  the  beginning  of  the  mutation  period  as 
the  time  when  the  latent  potentialities,  present  in  this 
period,  first  arose.  For  obviously  the  capacity  for  pro- 
ducing 0.  gig  as  has  not  been  a  property  of  all  the  an- 
cestors of  my  Lamarckiana;  it  must  have  arisen  at  some 
time :  and  similarly  with  the  other  species.  Are  these 
potentialities  as  old,  or  perhaps  even  older  than  La- 
marckiana itself  ?  Probably  not.  It  is  simpler  to  suppose 
that  they  either  arose  on  the  spot  where  they  first  ap- 
peared, or  a  little  earlier  in  the  life  of  the  species. 

I  call  the  origin  of  the  latent  potentialities.  Premuta- 
tion; the  mutations  themselves  are  only  the  expressions 
of  these.  One  of  the  objects  of  future  investigation 
ought  to  be  to  determine  the  essential  conditions  of  this 
premutation  and  if  possible  to  induce  it  at  will. 

Periods  of  mutation  must  occur,  or  at  any  rate  must 
have  occurred,  times  without  number,  in  nature.  For 
groups  of  allied  species,  which,  so  far  as  one  can  judge, 
are  related  to  one  another  exactly  as  my  Oenotheras  are, 
occur  throughout  the  animal  and  vegetable  kingdom. 
Wherever  the  constancy  of  the  characters  of  such  species 
has  been  established  in  cultures  they  constitute  the  es- 
peces  affines  of  Jordan.     I  have,  already,  often  men- 


Conclusion.  511 

tioned  Draha  verna,  Viola  tricolor,  HcliantJicmwn  vul- 
garc,  etc.  as  the  best  examples  of  these.  But  in  cases 
where  the  constancy  of  the  new  species  has  not  been  ex- 
perimentally tested,  or  where  their  study  has  been  made 
difficult  by  the  effects  of  natural  crossing,  we  get  the 
so-called  nebulous  groups  of  the  systematists  —  i.  e., 
groups  in  which  the  various  authorities  do  not  agree  with 
each  others'  diagnoses.  Salix,  Ruhus,  Rosa,  Hieraciimi 
are  the  most  familiar  examples  of  this  case. 

But  the  most  important  point  for  us  is  the  almost 
complete  agreement  between  the  new  Lainarckiana-grou\) 
and  the  old  biennis-gronp.  The  forms  of  the  latter,  re- 
garded by  some  authors  as  species  and  by  others  as 
varieties,  give  the  impression  of  being  the  remains  of  a 
previous  mutation  period.  They  obviously  belong  to- 
gether, differ  from  one  another  in  the  same  kind  of  way 
as  the  newer  species  do;  they  are  constant,  mutually 
fertile,  and  exhibit  transgressive  variability  in  many  of 
their  characters  in  such  a  way  that  at  first  sight  they 
do  not  seem  to  be  sharply  separated  from  one  another. 
Nevertheless  they  come  absolutely  true  from  seed. 

The  supposed  mutation  period  of  Oenothera  biennis 
must  obviously  have  taken  place  in  their  American  home : 
the  products  of  this  period,  the  Linnean  species  of  to-day, 
have  spread,  thence,  over  a  large  part  of  the  earth. 

And  if  we  give  the  rein  to  our  imagination  we  can 
conceive  each  genus  and  each  larger  group  as  being,  also, 
the  result  of  a  mutation  period. 


PART  III. 
NUTRITION  AND   SELECTION. 


, 


i 


I.     SIMULTANEOUS    INFLUENCE   OF    NUTRI- 
TION AND  SELECTION  ON  VARIOUS 
CHARACTERS. 

§   I.    VARIABILITY  AS  A  NUTRITIONAL  PHENOMENON. 

When  a  new  science  comes  into  the  field,  it  usually 
happens  that  certain  groups  of  phenomena,  which  uj)  to 
then  had  been  dealt  with  under  other  heads,  are  found 
to  come  within  its  ken.  This  is  happening  at  the  present 
moment,  with  the  study  of  variability  and  that  of  the 
dependence  of  the  growth  and  development  of  particular 
organs  and  characters  on  nutrition.  This  connection  with 
nutrition  has  been  studied  chiefly  from  the  experimental 
and  biological  point  of  view ;  whilst  the  same  phenomena 
have  been  dealt  with  by  statistical  methods  from  another 
point  of  view. 

New  boundaries  are  difficult  to  defiihe,  and  it  will  be 
a  long  time  before  an  agreement  will  l)e  reached  as  to 
which  sections  of  the  theory  of  nutrition  should  be  in- 
cluded in  the  science  of  variability. 

In  the  historical  and  critical  part  (Part  I,  i)p.  L^3  and 
137  etc.)  I  have  urged  that  we  had  no  right  to  give  up  the 
attempt  to  provide  an  answer  to  the  question  as  to  the 
causes  of  the  fluctuating  dififerences  between  individuals 
and  between  homologous  organs  of  one  and  the  same 
individual.     The  science  of  variabilitv  must  not  be  satis- 


516  Influence  of  Nutrition  and  Selection. 

fied  with  being  a  purely  descriptive  and  statistical  one; 
it  must,  like  every  other,  seek  to  determine  the  causes  of 
the  phenomena  of  which  it  treats. 

If  polymorphism  is  excluded  on  the  one  side  and 
mutability  on  the  other,  the  whole  range  of  variability 
can  be  described  in  terms  of  Quetelet's  law.  Then 
there  is  the  question  of  the  inheritance  of  these  varia- 
tions. The  deviations  of  the  various  individuals  from 
the  mean  are  heritable :  but  not  in  their  entirety ;  a  part 
is  always  lost.  Regression  always  takes  place,  and  this 
usually  involves  more  than  one-half  and  often  as  much 
as  two-thirds  of  the  original  deviation.  This  is  the 
source  of  the  third  principle  in  the  theory  of  variability : 
the  possibility  of  an  increase  of  the  deviation  by  means 
of  selection.  This  increase,  which  is  sometimes  spoken 
of  as  a  heaping  up  of  similar  small  differences,  leads  to 
the  so-called  accumulation  and  fixation  of  characters  and 
thus  to  the  production  of  improved  races. 

Exactly  the  same  deviations  from  the  mean  as  those 
with  which  statistics  have  made  us  familiar  may  be 
brought  about,  either  by  chance  or  by  deliberate  experi- 
ment, by  changes  in  the  conditions  of  nutriment.  Char- 
acters and  organs  whose  dimensions  may  be  increased  or 
diminished  by  selections,  are  also  dependent  on  the  con- 
ditions of  life  and  in  many  cases  it  is  very  difficult  to 
decide  which  of  the  two  causes  has  been  most  operative. 

The  recent  researches  of  Mac  Leod  and  others  clearly 
point  to  a  very  close  relationship  between  nutrition  and 
variability.  For,  broadly  speaking,  variability  is  really 
nothing  more  than  differences  in  individual  strength. 
The  stronger  a  plant  or  a  branch  on  a  plant  is,  the  greater 
is  the  likelihood  of  deviations  in  a  positive  direction ;  weak 


Variability  as  a  Nutritional  Phenomenon.       51/ 

plants  and  sickly  branches  tend  to  fluctuate  in  tlie  oppo- 
site direction. 

But  "individual  strength"  points  clearly  to  nutrition, 
if  we  use  this  word  in  its  widest  sense  and  especially  if 
we  make  it  include  the  better  opportunity  which  a  i)lant 
has  of  being  nourished,  as  when  it  has  plenty  of  room 
and  plenty  of  light,  and  so  forth. 

If  we  view  the  whole  field  of  nutritional  phenomena 
and  that  of  fluctuating  variability-^  they  appear  to  inter- 
lock only  to  a  certain  extent.  Many  statistical  inquiries 
point  as  little  in  the  direction  of  such  a  connection,  as 
the  excessively  vigorous  or  feeble  growth  of  weeds  and 
cultivated  plants  under  extreme  conditions  seem  to  point 
to  it.  But  indications  that  the  two  phenomena  are  in  fact 
connected,  are  by  no  means  lacking.  Goebel,  for  ex- 
ample, observed  that  in  Agrimonia  Eupatoriuni  the  lower, 
best  nourished,  flowers  of  the  inflorescence  had  many 
more  stamens  than  the  upper  more  feebly  nourished 
ones.-  In  the  sugar-beet  the  capsules  on  the  lower  part 
of  the  stem  contain  many  seeds ;  those  on  the  upper  part 
and  on  the  small  lateral  branches  contain  few,  and  often 
only  one.  Many  varietal  characters  answer  the  require- 
ments of  the  gardener  only  when  they  are  on  strong  in- 
dividuals; if  the  plants  are  weak  they  are  developed 
either  too  little  or  not  at  all  (e.  g.  Cclosia  cristata). 

We  must  make  it  our  business  therefore,  on  the  one 
hand,  to  study  the  results  of  increased  and  diminished 
nutrition,  by  statistical  methods;  and  on  the  otlier  to 
deal  with  the  conditions  affecting  the  different  groups 
of  individuals,  when  studying  Quetelet's  curves. 

An  inquiry  of  this  kind  will  at  any  rate  have  one 

^  See  C.  Fruwirth,  Die  Zikhtuug  dcr  landicirthschaftlichcn  Cul- 
turpHancen,  igoi. 

^  GoEBEL,  Bot.  Zcitung,  1882,  p.  357- 


518  Influence  of  Nutrition  and  Selection. 

good  result :  it  will  bring  out  more  prominently  the  fun- 
damental distinction  between  variability  and  mutability. 
There  are  still  so  many  cases  in  which  it  is  difficult  or 
even,  for  the  present,  impossible  to  define  the  limits  be- 
tween these  fundamentally  different  principles,  that  every 
contribution  to  a  solution  of  the  problem  is  of  value. 

Therefore  it  is  most  essential  from  the  point  of 
view  of  the  theory  of  mutability  to  have  a  perfectly  clear 
conception  of  the  nature  of  variabilit}^  in  the  narrower 
sense  of  the  term.  Absolute  constancy  and  high  varia- 
bility are  regarded  by  many  as  diametric  opposites;  in 
fact  it  is  believed  by  those  who  hold  the  modern  theory 
of  selection,  that  variability  leads  to  inconstancy,  that 
is  to  say  to  the  production  of  new  forms.  According 
to  the  mutation  theory  however  constancy  and  variability 
are  perfectly  compatible  and,  in  most  cases,  usually  asso- 
ciated. That  which  is  constant  is  the  type  or  mean,  on 
both  sides  of  which  fluctuations  may  occur. 

The  ray  florets  of  the  common  cornflower  are  variable 
in  number ;  the  weaker  the  plant  or  branch  the  smaller  is 
this  number,  according  to  Mac  Leod.^  The  secondary 
fruits  of  Papaver  somniferum  polycephalum  exhibit  the 
same  correlation,^  the  tongue-florets  in  the  heads  of 
Othonna  crassifolia  diminish  if  the  nutrition  of  the  plant 
is  artificially  curtailed.^  '  The  same  thing  happens  in 
Chrysanthemum  segetum"^  and  other  Composites.''^     And 

^  Page  135  of  this  book.  ^  Pages  138-143. 

'  Page  147  and  Othonna  crassifolia  in  Kruidkundig  Jaarboek, 
Gent,  1900,  p.  20. 

*  Over  het  periodisch  optreden  van  anomaHen,  Kruidkundig  Jaar- 
boek Dodonaea,  T.  XI,  1899,  p.  54;  Sur  la  periodicite  des  anomalies 
dans  les  plantes  monstrucuses,  Archiv.  Neerland.  d.  Sc.  exactes  et 
nat.,  2d  Series,  T.  3,  p.  403.  Ueber  Curvenselection  bei  Chrysanthe- 
mum segetum,  Berichte  d.  d.  bot.  Ges.,  Bd.  XVII,  1899,  p.  84;  Ueber 
die  Periodicitdt  der  partiellen  Variationen;  ibid.,  Bd.  XVII,  p.  45. 

^  A.  Weisse^  Die  Zahl  der  RandblUthen  am  Compositenkopfchen, 


Variability  as  a  Nutritional  Phciionicnon.       519 

we  can  easily  observe  that  in  the  Um1)clH  ferae  tlie  num- 
ber of  umbels  is  small  in  proportion  as  the  twif,^  bearing 
them  is  weak. 

>  With  regard  to  Papavcr  somnifernm  polyccphaliim 
we  saw  in  the  first  part  that  it  was  not  possible  to  separate 
selection  from  nutrition.  I  mean,  if  we  choose  our  seed- 
parent,  paying  attention  to  the  greater  or  less  beautiful 
development  of  the  circlet  of  secondary  fruits,  we  in- 
evitably chose  either  the  strongest  or  the  weakest  ]jlants. 
There  seems  therefore  no  escape  from  the  conclusion  tbat 
the  variability  of  this  circlet  is  simply  a  plienomenon  of 
nutrition  and  that  selection  in  one  direction  merely 
chooses  the  most  highly  nourished  individuals ;  and  in  the 
other,  the  most  poorly  nourished. 

In  an  investigation  of  this  kind  one  must  take  into 
account  the  susceptible  period.  One  organ  will  pass 
through  this  period  earlier;  another  later,  as  I  have 
pointed  out  in  the  case  of  the  poppy  referred  to.  The 
same  is  true  of  oats  and  wheat  in  relation  to  the  amount 
of  water  in  the  soil.  In  the  first  vegetation-period  this 
condition  influences  the  number  of  internodes  in  the 
haulm  as  well  as  in  the  panicles,  or  ears.  At  the  time 
of  shooting,  the  amount  of  water  in  the  ground  afifects 
the  length  of  the  internodes,  and  the  size  of  the  parts  of 
the  inflorescence  (the  foundations  of  which  have  already 
been  laid  down  by  this  time)  as  well  as  the  greater  or 
less  fertility  of  the  ears.  Much  water  at  the  time  of 
shooting  increases  the  amount  of  straw  as  well  as  the 
yield  in  grain.  ^ 

Jahrb.  f.  w.  Bot.,  Bd.  30,  1897,  p.  453  and  W.  Haacke.  Ilnhciikcluui:s- 
mechanische   Untersuchungcn,  Biol.  Cenlralbl.,   1900. 

^VoN  Seelhorst,  Journal  fiir  Landwirthschaft,  Bd.  4S.  p.  163: 
Reference  in  Botan.  Ccntralbl,  1900,  No.  41,  Bd.  84,  p.  54. 


520  Influence  of  Nutrition  and  Selection. 

The  truth  of  the  theory  put  forward  by  Schindler 
and  Von  Proskowetz  that  it  is  impossible  to  unite  many 
good  quahties  in  one  individual,  depends  partly  on  the 
absolute  productive  capacity  and  partly  on  the  correct 
nourishment  of  the  individual  qualities  at  the  sensitive 
period  of  their  development.  Johannsen's  exhaustive 
and  epochmaking  researches  into  the  correlation  between 
seed-weight  and  nitrogenous  contents  of  barley  point  in 
the  same  direction.  The  heavier  the  grain  the  greater 
is  the  amount  of  nitrogen  Vv^hich  depreciates  the  value 
of  the  grain.  ^  Evidently  both  vary  in  the  same  direc- 
tion under  the  influence  of  high  nutrition.  But  if  the 
sensitive  periods  for  the  two  should  not  coincide,  the 
supply  of  nutriment  might  be  so  managed  that  the  weight 
of  the  seed  is  increased  without  effecting  a  corresponding 
increase  in  those  constituents  of  the  seed  which  are  rich 
in  nitrogen.  At  present  it  is  not  possible  to  do  this 
directly,  but  Johannsen  succeeded  in  getting  a  much 
better  harvest  without  having  increased  its  proportion  of 
nitrogen,  by  selecting  the  one  value  in  a  positive  direc- 
tion and  the  other  in  a  negative  one. 

A  further  series  of  experiments  is  necessary  before 
the  conclusions  (important  alike  to  the  pure  and  applied 
biologist)  based  on  these  remarkable  results  can  be  re- 
garded as  thoroughly  established.  I  am  simply  using 
them  here  as  a  proof  of  the  relation  between  nutrition 
and  selection  in  general. 

For  there  is  yet  another  method  of  studying  the  re- 
lation between  manuring  and  selection.  We  can  alter 
both  factors;  and  allow  them  to  operate  either  in  the 

*W.  Johannsen,  Ueher  die  VariahiUtat  der  Gerste  mit  heson- 
dercr  Ri'icksicht  auf  das  Verhaltyiiss  zwisclien  Korncrgewiclit  und 
Stickstoffprocent.  Meddelelser  fra  Carlsberg  Laboratoriet,  Bd.  4, 
Heft  4,  1899. 


Variability  as  a  Nutritional  Phenomenon.       521 

same  or  in  opposite  directions.  We  can,  so  to  speak, 
add  their  effects  or  subtract  the  one  from  the  other.  If 
this  experiment  succeeds  it  proves  that  the  two  plienom- 
ena  are  of  the  same  order,  and  suggests  a  method  of 
determining  their  relative  importance. 

I  shall  therefore  describe  in  this  chapter  a  series  of 
experiments  carried  out  on  this  principle.  They  deal 
with  measurable  or  countable  characters  which  are  ca- 
pable of  experimental  as  well  as  of  statistical  treatment. 
I  chose  for  this  purpose  the  length  of  the  fruits  of  the 
ordinary  Oenothera  Lamarckiana  (Figs.  114  and  115, 
pp.  529  and  530),  and  also  the  material  employed  by 
LuDWiG  which  is  afforded  by  the  ray  florets  of  Compo- 
sites and  the  rays  in  the  umbels  of  Umbelliferae  (Figs. 
117-119,  pp.  561-565).  In  the  case  of  the  fruits  I  tried 
both  the  addition  and  subtraction  of  the  factors ;  but  in 
that  of  the  ray-florets  and  the  rays  of  the  umbels  only 
the  simultaneous  operation  in  opposite  directions  of  heavy 
manuring  and  negative  selection.  The  result  of  the  ex- 
periment was  that  sometimes  the  one  factor  and,  at  other 
times,  the  other  predominated. 

The  inquiry  into  the  effect  of  nutrition  (manuring, 
plenty  of  room,  light  and  water,  etc.)  has  led  to  the  dis- 
covery of  two  principles  (foreshadowed  in  the  discus- 
sions in  the  first  section  p.  137)  which  I  think  ought 
to  be  enunciated  here  in  the  interest  of  a  clear  under- 
standing of  the  whole  range  of  phenomena. 

These  two  principles  are  the  following: 

1.  The  younger  a  plant  is  the  greater  is  the  influence 
of  external  conditions  on  its  variability,  that  is,  on  the 
place  which  its  various  characters  will  occupy  in  the 
curves  of  variability  of  the  wdiole  culture  or  race. 

2.  In  connection  with  this  principle  the  nutrition  (^f  the 


522  Influence  of  Nutrition  and  SetectioH. 

seed  on  the  motherplant  has,  in  many  cases  at  any  rate,^ 
a  greater  effect  on  variabihty  than  nutrition  during  ger- 
mination and  vegetative  Hfe  itself. 

It  seems  to  me  that  these  principles  which  I  only 
appreciated  after  many  years  of  experimenting,  are  now 
perfectly  clear  and  evident. 

From  these  principles  there  follows  the  experimenta' 
method  which  I  call  the  Principle  of  the  manuring  of  ihc 
parent-plant.  That  is  to  say,  the  effect  of  manuring 
on  variability  must  be  studied  not  only  on  the  plants 
which  have  been  heavily  manured,  but  mainly  on  the 
generation  produced  by  their  seeds. 

These  principles  lead  to  a  further  problem,  the  solu- 
tion of  which  will  perhaps  be  of  great  importance  from 
the  point  of  view  of  the  theory  of  selection.  For  it  is 
clear  that  the  principle  of  the  manuring  of  the  parent- 
plants  is  not  necessarily  confined  to  one  generation.  We 
shall  obviously  not  get  the  best  nourished  seeds  from  ill 
favored  parents;  that  is  from  parents  which  have  them- 
selves arisen  from  poor  seeds.  On  the  contrary  the 
operation  of  high  nutrition  of  the  seeds  must  be  capable 
of  accumulation  through  two  or  more  generations.  The 
same  is  true  of  low  or  defective  nutrition.  But  inasmuch 
(as  a  general  rule)  those  individuals  which  exhibit  the 
character  dealt  with  in  a  high  degree  are  the  best  nour- 
ished we  naturally  choose  the  most  highly  nourished 
individuals  as  seed-parents  when  we  are  selecting  for  any 
particular  character.  In  the  course  of  generations  the 
effect  of  nutrition  accumulates,  and  in  this  way  the  devia- 
tion of  the  particular  character  from  the  original  type  is 
continuously  increased.     The  question  arises  therefore : 

^  Sometimes,  however,  a  greater  effect  can  be  produced  on  varia- 
tion by  a  good  or  bad  treatment  of  the  seedhngs  than  by  the  choice 
of  seeds ;  for  example  in  Papaver  somniferum  polycephalum. 


Methods  of  Investigation.  523 

what  part  6i  the  result  of  selection  is  due  to  this  accumu- 
lation  of  nutrition   during  the  succeeding  generations? 

These  considerations  tend  to  draw  selection  and  nutri- 
tion closer  and  closer  together.  The  exact  morle  of 
nutrition  seems  to  me  a  matter  of  secondary  importance; 
what  is  of  the  first  importance  is  to  discover  tlie  effects 
of  nutrition  on  the  susceptible  periods  in  development, 
and  to  study  the  accumulation  of  this  effect  in  the  course 
of  some  generations.  Now,  just  as  nutrition  reaches  its 
maximum  effect,  in  practice,  in  the  course  of  a  few  gen- 
erations, so  the  limit  reachable  by  selection  is  very  soon 
attained.^  The  significance  of  the  parallel  between  these 
two  limits  seems  to  me  to  be  obvious. 

The  closer  variability  is  drawn  towards  nutrition  the 
wider  becomes  the  gulf  between  variability  and  muta- 
bility. 


§  2.  METHODS  OF  INVESTIGATION. 

The  effect  of  nutrition  and  selection  can  either  be 
exerted  in  similar  or  in  opposite  directions;  the  sum  of, 
or  the  difference  between,  their  effects  can  thus  be  de- 
termined. 

The  general  effect  of  both  factors  is  well  known.  We 
are  not  concerned  to  prove  that  the, effect  of  high  nutri- 
tion is  to  produce  large  fruits,  and  that  that  of  insuffi- 
cient manure  is  to  produce  small  ones,  and  so  forth.  It 
seems  more  important  to  show  that  the  number  of  ray- 
florets  can  either  be  increased  or  diminished  by  selection  : 
but  even  on  this  point  there  is  no  doubt  whatever.  11ic 
only  question  is  which  of  these  two  factors  will  pre- 
ponderate in  given  instances? 

'  Part  I,  §  9,  p.  85. 


524  Influence  of  Nutrition  and  Selection. 

The  experimental  part  of  the  work  is  to  provide  the 
nutrition,  i.  e.,  generally  favorable  conditions  of  culti- 
vation. The  results,  however,  have  to  be  dealt  with  by 
statistical  methods  which  were  originated  by  Quetei.et 
and  Galton^  and  have  been  developed  in  recent  years 
amongst  others  by  Pearson,  Ludwig,  Duncker,  Daven- 
port and  Amann.^ 

Let  us  begin  with  the  latter  point  and  let  us  seek  to 
delineate  the  main  features  of  this  method  in  a  few  short 
paragraphs  in  order  that  we  may  have  a  clear  idea  of  the 
manner  in  which  they  are  employed.  I  have  chosen  Gal- 
TON^s  method  as  the  simplest  and  most  convenient  for  the 
latter  purpose. 

Ouetelet  and  Galton  have  shown  that  the  indi- 
vidual  variations  of  men  and  other  animals  follow  the 
laws  of  probability.  The  deviations  from  the  type  of  any 
fluctuating  character  can  be  expressed  by  a  curve  since 
they  are  grouped  symmetrically  round  the  type  as  a  center 
of  greatest  density.  The  more  numerous  the  observa- 
tions the  more  exactly  does  the  curve  of  variability  coin- 
cide with  the  curve  of  probability.  The  cause  of  this 
parallel  is,  pretty  obviously,  that  the  various  deviations 
from  the  normal  are  determined  by  a  vast  number  of  ex- 
ternal and  internal  influences. 

Quetelet  asserted  that  the  above  law  applied  to 
plants  and  Galton  demonstrated  it  by  a  few  experi- 
ments. My  cultures  of  races  and  varieties  extending,  as 
they  have  done,  over  many  years,  have  given  me  plenty 


^  Galton's  Natural  Inheritance  is  indispensable  for  a  proper 
understanding  of  the  foundations  of  this  method  and  the  reader  is 
advised  to  refer  to  it  in  conjunction  with  this  chapter. 

^My  experiments  were  made  in  1892- 1894,  i-  e.,  before  the  pub- 
lications of  these  authors  had  appeared. 


Methods  of  Investigation. 


525 


of  opportunity  of  convincing  myself  of  its  general  ap- 
plicability in  the  vegetable  kingdom.^ 

When  it  is  once  proved  that  the  form  of  the  emi)irical 
curve  of  fluctuations  in  plants  coincides  with  that  (jf  the 
theoretical  curve  of  probability,  so  far  as  unavoidable 
errors  in  observation  permit,  the  properties  of  the  latter 
may  evidently  be  ascribed  to  the  former. 

The  most  important  property  of  the  curve  for  our 
purposes  is  that  it  may  be  definitely  descril^ccl  by  two 
magnitudes,  (I)  the  mean  value  of  the  character  in  ques- 
tion and  (II)  the  amplitude  or  extent  of  variation.  The 
mean  value  used  by  Galton  is  that  magnitude  which  half 
of  the  individuals  exceed,  but  which  the  other  half  do  not 
attain.  This  he  calls  the  median.  It  need  not  be  a  mag- 
nitude which  actually  exists,  but  is  found  by  interpola- 
tion on  the  assumption  that  variation  is  unbroken  and 
continuous. 

Galton 's  median  can  be  determined  more  easily  than 
the  ordinary  mean,  which  is  obtained  by  dividing  the  sum 
of  all  values  by  the  number  of  observations.  It  has 
exactly  the  same  justification  and  in  symmetrical  curves 
the  two  necessarily  coincide. 

The  second  factor  is  the  amplitude  of  variation  which 
finds  its  simplest  expression  in  the  remoteness  of  the  ex- 
treme variants,  provided  that  the  number  of  individuals 
is  not  too  small.  But  the  raritv  of  these  extremes  makes 
the  determination  of  these  limits  by  their  simple  observa- 
tion largely  a  matter  of  chance.  Galton  therefore  uses 
another  value  borrowed  from  the  theory  of  prol)ability, 
as  a  measure  of  the  amplitude.  This  is  the  magnitude  of 
the   deviation   from  the  mean  which   is  exceeded   by  a 

^  See  Ber.  d.  d.  Bot.  Gcsellsch.,  Bd.  XTT.  1894.  p.  197.  wlicrc  lie 
previous  literature  is  cited. 


526  Influence  of  Nutrition  and  Selection. 

quarter  of  the  individuals  and  therefore  analogous  to  the 
so-called  ''probable  error."  He  calls  it  the  Ouartile  (Q). 
There  is  obviously  one  quartile  on  either  side  of  the 
Median  (M)  ;  these  are  called  Qi  and  Q2.  If  the  curve 
is  symmetrical,  the  two  quartiles  have  the  same  value; 
otherv^ise  the  dissimilarity  of  the  empirically  determined 
Qi  and  Qo  is  a  measure  of  the  degree  of  symmetry  of  the 
curve.  If  the  difference  between  the  two  is  within  the 
range  of  the  error  of  observation,  their  mean  value 
Q=(Qi  +  02)/2  is  the  measure  of  the  amplitude  of 
variation  of  the  material  under  consideration. 

If  we  wish  to  compare  the  amplitude  for  different 
characters  together  we  must  reduce  them  to  a  common 
measure.     This  is  done  by  dividing  Q  by  M /^ 

We  see  therefore  that  Qi,  M  and  Q2  are  the  numbers 
which  have  to  be  determined  by  observation.  The  form 
of  the  curve  is  determined  by  them  and  any  differences 
between  the  curves  so  determined  and  the  actual  figures 
themselves  must  be  ascribed  to  errors  in  observation,  at 
any  rate  in  symmetrical  curves.  The  greater  the  number 
of  observations  which  go  to  make  a  curve  the  smaller 
will  these  differences  be. 

In  the  following  sections  I  shall  deduce  these  val- 
ues from  the  data ;  and  use  them  as  a  basis  for  discussion. 
One  advantage  of  this  will  be  that  it  will  render  drawings 
of  the  curves  superfluous,  or  at  any  rate  only  useful  for 
the  purpose  of  demonstration;  and  that  it  will  compress 
the  numerical  material  into  a  few  figures. 

A  few  remarks  on  the  subject  of  construction  of  these 
curves  (Figs.  115-118)  are  called  for.  The  number  of 
ordinates  is  by  no  means  necessarily  the  same  as  the 

*  Ed.    Verschaffelt,    Ueher   graduelle    VariahiUt'dt   von   pUans-, 
lichen  Eigenschaften,  Ber.  d.  d.  bot.  Gesellsch.,  Vol.  XII,  1894,  p.  350. 


Methods  of  Investigation.  527 

number  of  groups  in  the  tables.  This  is  sufficiently  evi- 
dent where  we  are  dealing  with  continuous  variations 
such  as  length.  For  here  the  unit  chosen  is  quite  an  arbi- 
trary one.  For  example,  if  I  had  measured  the  fruits  of 
Oenothera  accurately  to  tzvo  millimeters  only  {or  if  I 
had  measured  them  in  English  inches),  I  should  have 
had  fewer  ordinates;  but  if  I  had  measured  them  to  half 
a  millimeter,  I  should  have  had  twice  as  many.  And  in 
dealing  with  ray-florets  we  may  consider  units  or  pairs 
or  larger  groups.  In  fact  the  data  may  be  grouped  in 
any  desired  way,  to  suit  our  purposes. 

The  number  of  units  to  be  used  in  the  construction  of 
a  curve  depends  in  principle  on  the  number  of  individuals. 
If  this  is  small,  they  must  be  made  correspondingly  few. 
In  order  to  do  this  the  two  or  three  groups  of  figures,  in 
the  midst  of  which  the  interpolated  value  of  M  lies,  are 
united  to  form  a  single  ordinate;  this  forms  the  apex  of 
the  curve.  We  then  deal  with  the  groups  to  the  right  and 
to  the  left  of  it  in  the  same  way.  This  is  the  only  way  in 
which  the  peaks  and  valleys,  in  the  curve,  resulting  from 
an  insufficient  number  of  observations  can  be  smooth.ed 
away. 

Finally,  if  the  various  curves  are  to  be  compared  with 
one  another,  the  empirical  data  must  of  course  be  reduced 
to  percentages. 


11.    THE  LENGTH   OF   THE   FRUIT   IX   OENO- 
THERA LAMARCKIANA. 

§  3-   CORRELATION    BETWEEN   INDIVIDUAL   STRENGTH 

AND  LENGTH  OF  FRUIT. 

Let  us  now  consider  the  relation  between  the  indi- 
vidual strength  of  the  plant  and  a  character  which  can 
be  conveniently  studied  by  statistical  methods ;  partly  as 
an  example  of  the  method  of  dealing  with  measurements, 
described  in  the  preceding  chapter ;  and  partly  on  account 
of  the  importance  of  the  question  itself.  For  this  purpose 
I  have  chosen,  as  I  indicated  in  the  previous  section,  the 
length  of  the  ripe  fruits  of  our  Evening  Primrose  (Fig. 
114). 

These  fruits  are  highly  variable,  not  only  in  plants 
treated  differently  but  also  in  the  various  individuals  of 
the  same  culture.  It  is  not  difficult,  as  a  rule,  to  find 
among  the  longest  ones  individuals  which  have  twice  the 
length  of  the  shortest  ones  (Fig.  114  A  and  C).  Such 
fruits  are  however  very  rare;  the  intermediate  ones  (Fig. 
114  B)  are  always  by  far  the  commonest.  In  sorting 
such  material  we  easily  find  that  the  frequency  of  the 
various  values  is  describable  in  terms  of  the  Quetelet- 
Galton  law,  especially  when  the  number  of  plants  meas- 
ured is  large. 


Individual  Strength  and  Length  of  Fruit.        529 

Fig.  1151  exhibits  these  values  grapliically.  The  meas- 
urements were  made  on  568  plants;  and,  in  each  case,  the 


Fig.  114.  OetiotJicra  iMmarckiana.  Lower  sections  of  three 
fruit  bearing  stalks  taken  from  the  main  stems  of  three 
plants,  natural  size.  A,  small;  B,  median;  C,  long  fruits. 
Culture  of  1899. 

lowest  ripe  fruit  was  measured.     Hie  lengths  of  these 

fruits  ranged  between   15  and  34  millimeters,  and  their 

^  Ueher  halhe  Galtonctirvcn  als  Zcichcn  discontinuirlichcr  I'ana- 
tion,  Ber.  d.  d.  Bot.  Gesellsch.,  Bd.  XII,  1894,  Tabic  X,  Fig.  i.     I  he 


530  Length  of  the  Fruit  in  Oenothera  Lamarckiana. 


mean  length  was  24  millimeters.  They  agree,  as  a  com- 
parison with  the  dotted  line  shows,  fairly  exactly  with  the 
probability  curve. 


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bh  rt  UG  S 


If  we  calculate  the  values,  which  we  described  in  the 
preceding  paragraph,  from  these  data  we  get  the  follow- 
ing, in  millimeters : 

Minimum  Qo  M  Qp         Maximum 

34 


15 


22.2 


24.1 


26.1 


data  for  this  curve  appear  on  page  200.  This  curve  v^^as  the  first  to 
demonstrate  the  appHcability  of  the  Quetelet-Galton  law^  to  the 
vegetable  kingdom. 


Individual  Strength  and  Length  of  Fruit.        531 

Maximum  and  minimum  simply  refer  to  the  len^^h 
of  the  longest  and  shortest  fruits.  M  is  Galton's  methan 
or  the  mean — the  value  of  which  half  tlie  individuals  do 
not  attain,  but  is  exceeded  by  the  other  half. 

This  median  is  found  by  interpolation,  on  the  assump- 
tion that  the  fruits  measured  as  24  mm.  varied  contin- 
uously between  23.5  and  24.5  mm.  Qo  and  Qp  are  the 
ordinates  which  are  separated  from  M  by  a  quarter  of 
all  the  individuals  in  each  case.  They  are  also  found  by 
interpolation. 

Galton^s  quartiles  are  therefore:  Qi  =  M — Qo  and 
Q^  =  Qp—M.  Further  (Oi  +  Q2)/2  =  Q  is  the  measure 
of  the  amplitude  of  the  curve.  Lastly  Q/M  is  a  measure 
of  this  value  independent  of  the  size  M  and  of  the  nature 
of  the  variable  character;  a  number  therefore  by  means 
of  which  the  variation  of  the  fruit  length  in  Oenothera 
may  be  compared  with  the  variation  of  other  characters 
in  other  plants. 

These  values  calculated  from  the  above  data  are  as 
follows : 

Qt  Q2  Q  % 

1.9  2.0  1.95  0.08 

In  the  description  of  the  experiment  Qo  and  Qp  can 
be  omitted,  now  that  the  values  0\,  M  and  O2  have  been 
calculated  from  the  empirical  data. 

A  greater  degree  of  accuracy  can  be  attained  in  these 
investigations  by  determining  the  mean  length  of  the 
fruits  on  a  given  plant  instead  of  determining  that  of  a 
single  fruit  only.  The  question  then  arises :  from  how 
many  fruits  should  this  mean  value  be  calculated.  I  ha\e 
measured  five;  and  in  this  section  and  in  the  following 
one  I  have  used  the  mean  of  the  lengths  of  the  lowest 


532  Length  of  the  Fruit  in  Oenothera  Lamarckiana. 

five  good  fruits  as  a  measure  of  the  length  of  fruit  in 
each  individual. 

The  reasons  which  led  me  to  this  choice  are  the  fol- 
lowing. My  selection  was  always  an  individual  one ; 
that  is  to  say  I  did  not  search  for  the  longest  and  shortest 
fruits  in  the  harvest,  but  for  the  individuals  the  mean  of 
whose  fruits  was  the  longest,  and  for  those  the  mean  of 
whose  fruits  was  the  shortest.  But  on  each  inflorescence 
the  size  of  the  fruits  gradually  decreases  from  below  up- 
wards with  the  gradual  exhaustion  of  the  plant.  Lateral 
branches  often  have  small  capsules ;  but  as  a  rule  I  did 
not  allow  these  to  develop ;  I  simply  broke  them  off  quite 
young.  For  that  was  the  only  way  in  which  it  was  pos- 
sible to  grow  a  large  number  of  healthy  plants  on  the 
relatively  small  space  at  my  disposal. 

The  mean  length  of  the  five  lowest  fruits  is  obviously 
more  or  less  an  arbitrary  measure  of  the  mean  length 
of  the  fruit  of  a  plant.  It  would  be  more  accurate  to 
measure  ten  or  twenty  fruits.  We  cannot  count,  with 
sufficient  certainty,  on  more  than  twenty  ripe  fruits  per 
plant;  many  individuals  do  not  bear  so  many;  for  the 
flowers  which  open  after  the  first  of  September  usually 
do  not  ripen  their  fruits  with  us.  To  measure  the  mean 
length  of  all  the  fruits  on  a  plant,  all  the  lateral  branches 
would  have  to  flower,  and  measurements  would  have  to 
be  made  of  the  ripe  fruits  of  all  the  flowers.  But  this 
is  absolutely  impossible ;  at  least  in  our  climate,  and  when 
the  plants  are  cultivated  as  annuals. 

Fortunately  the  measurements  of  the  five  lower  fruits 
gives  figures  the  accuracy  of  which  is  sufficient  for  our 
experiment.  In  order  to  prove  this  statement  by  a  direct 
experiment  I  took  2>d>  plants  in  November  1 893  and  meas- 


Individual  Strength  and  Loujth  of  Fruit.        533 

iired  the  mean  length  of  the  lower  five  and  of  the  luwer 
twenty  fruits  on  them. 

The  mean  length  of  the  fruits  is  found  by  dividing 
the  sum  of  their  lengths  by  the  number  of  fruits  meas- 
ured. For  this  purpose  the  fruits  were  cut  tlirough  just 
at  their  base  (which  is  marked  at  its  point  of  junction 
with  the  bract  by  a  constriction,  so  that  the  measure- 
ments could  always  be  taken  from  a  fixed  point),  laid 
one  after  another,  end  on  end,  in  a  row,  great  care  being 
taken  in  arranging  them;  and  the  length  of  the  wliole 
series  was  read  off.  In  this  way  a  greater  exactitude  of 
the  measurements  is  attained,  whilst  only  one  measure- 
ment is  necessary  for  each  plant. 

Let  us  choose  an  example.  On  one  plant  the  total  of 
the  lengths  of  the  five  lower  fruits  was  167  mm.,  that 
of  the  twenty  lower  fruits  688.  The  mean  numbers  were 
therefore  33.4  and  34.4.     The  difference  is  1.0  mm. 

In  this  way  the  differences  for  the  38  plants  were 
determined;  some  were  positive,  others  negative.  Neg- 
lecting the  sign  the  differences  were  now  written  in  a 
series  in  order  of  magnitude.  The  result  was  that  in 
half  the  individuals  the  difference  was  less  than  1.25, 
but  in  the  other  half  greater.  In  one  case  only  (hd  it 
reach  as  much  as  4  mm.  The  probable  error  is  therefore 
1.25. 

In  other  words:  In  the  highly  improbable  case  of  all 
the  differences  being  positive,  or  all  negative,  the  figures 
in  our  table  would  have  been  1.25  mm.  more  accurate  if 
I  had  alwavs  measured  20  instead  of  5  fruits.  Differ- 
ences  of  1.25  and  less  must  therefore  be  regarded  as 
within  the  limits  of  errors  of  observation.  The  difi'cr- 
ences  occurring  in  the  experiments  to  be  described  are,  as 


534  Length  of  the  Fruit  in  Oenothera  Lamarckiaiia. 

a  matter  of  fact,  almost  without  exception  considerably 
larger. 

With  a  view  to  studying  the  correlation  between  indi- 
vidual strength  and  length  of  fruit^  I  also  measured,  on 
the  same  38  plants,  the  length  and  thickness  of  the  stem 
and  the  thickness  of  the  fruits.  The  thickness  of  the 
stem  was  measured  just  above  the  root  and  round  the 
lowest  fruit-bearing  internode.  The  length  of  the  stem 
was  complicated  by  other  factors ;  the  plants  which  came 
up  late  were  abnormally  elongated  because  the  light  was 
kept  off  them  by  their  taller  neighbors.  I  shall  therefore 
not  deal  further  with  this  character. 

The  data  are  summarized  in  the  table  below.   This  has 


CORRELATION  BETWEEN  THICKNESS  OF  STEM  AND  LENGTH 
OF  FRUIT  IN   OENOTHERA  LAMARCKIANA. 


THICKNESS  OF  STEM 

MEAN 
THICKNESS 

MEAN 
LENGTH  OF 

NUMBER 

OF 

BELOW 

ABOVE 

OF  FRUIT 

FRUIT 

INDIVIDUALS 

16 

12 

3.85 

38.6 

2 

15 

9 

3.5 

35.0 

2 

14 

9 

3.7 

31.8 

2 

12 

8 

3.5 

34.1 

3 

11 

9 

3.2 

30.2 

2 

11 

8 

3.3 

32.7 

2 

11 

7 

3.4 

31.6 

3 

10 

8 

3.1 

31.9 

2 

10 

7 

3.0 

30.6 

9 

9 

7 

2.9 

29.2 

2 

8 

7 

3.1 

29.7 

3 

8 

6 

3.0 

29.9 

3 

7 

5 

3.1 

30.1 

3 

^  The  method  of  measuring  and  estimating  correlations  between 
variable  organs  was  originated  by  Galton.  See  Correlations  and 
their  Measurements.  Proc.  Royal  Soc.,  Vol.  45,  (1888),  p.  135.  See 
also  Galton,  ibid.,  Vol.  40,  p.  42  and  Weldon,  ibid.,  Vol.  51,  (1892), 
page  3. 


Individual  Strength  and  Length  of  Fruit.       535 

been  condensed  by  uniting  the  Individuals  with  simihir 
thickness  of  stem,  and  by  giving  the  mean  length  of  theii 
fruits.  The  number  of  individuals  per  group  is  given  in 
the  last  column.  The  length  and  thickness  of  the  fruil 
was  measured  on  the  lowest  20  fully  developed  fruits  in 
the  case  of  each  individual  in  the  manner  described  above. 
All  the  values  are  expressed  in  millimeters. 

The  table  brings  out  the  strong  correlation  existing 
between  thickness  of  stem  and  thickness  and  length  of 
fruits.  For,  apart  from  negligible  individual  differences, 
the  fruits  are  longer  and  thicker,  the  thicker  the  stem 
is.  These  figures  are  not  sufficiently  extensive  for  the 
determination  of  Galton's  value  r;^  but  they  serve  their 
immediate  purpose  well  enough. 

Taken  in  conjunction  with  the  rest  of  what  we  know 
about  nutrition  and  growth  in  our  plant  they  tell  us  that 
as  a  rule  the  fruits  are  longer,  the  more  vigorous  the 
plant  is,  and  especially  that  the  longest  fruits  are  only 
found  on  the  strongest  plants.  Selection  in  the  direction 
of  long  fruits  therefore  chooses  the  strongest  plants 
whilst  selection  in  the  opposite  direction  must  choose  the 
weakest.^ 

It  should  be  mentioned  here  that  manuring  and  the 
choice  of  good  seed  are  not  the  only  methods  of  ensuring 
the  vigor  of  a  plant.  The  distance  of  the  plants  from  one 
another,  especially  in  youth,  plays  a  very  prominent  part 
in  determining  this.  Plants  standing  alone  usually  grow 
up  very  luxuriantly;  the  more  plants  one  grows  per 
square  meter  the  less  vigorous  are  they.  Another  method 
of  effectively  increasing  the  individual  strength  of  the 

^  r  =  ratio  =  measure  of  correlation. 

^  It  will  be  seen  that  this  generalization  agrees  perfectly  with  the 
considerations  set  forth  in  the  critical  part  of  this  work.  Cf.  in  this 
respect,  Papaver  somnifcrum  polyccphalum,  pp.  137-140. 


536  Length  of  the  Fruit  in  Oenothera  Lamarckiana. 

plant — the  culture  of  seedlings  in  pots —  will  be  described 
in  the  next  section. 


§  4.    THE  SIMULTANEOUS  OPERATION  OF  NUTRITION 

AND  SELECTION. 

The  length  of  the  fruits  of  the  large-flowered  Even- 
ing Primrose   (Figs.   114  and  115)   will  afford  suitable 


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material  with  which  to  gain  an  insight  into  the  interaction 
between  nutrition  and  selection.   With  regard  to  nutrition 

*The  curve  is  constructed  from  the  tables  given  in  the  text  by 
reducing  the  number  of  ordinates  to  one-half.     All  figures  are  con- 


The  Operation  of  Nutrition  and  Selection.       537 

I  have  confined  myself  to  positive  changes,  but  with  re- 
gard to  selection  to  both  positive  and  negative  ones;  and 
I  have  also  studied  the  effect  of  high  nutrition  continued 
through  a  number  of  generations  without  selecti(jn. 

High  nutrition  has  proved  itself  superior  to  the  most 
stringent  selection  (Fig.  116).  Even  when  combined 
with  negative  selection  it  has  improved  the  mean  H^ig. 
116B)  and  positive  selection  has,  in  combination  with  it. 
only  been  able  to  achieve  very  little  more  (Fig.  116Cj. 
And  without  any  selection  at  all  an  exceptionally  high 
nutrition  has  had  a  far  better  result  than  the  first  two 
combinations  (Fig.  116  D). 

Fig.  116  shows  the  main  result  of  this  whole  series 
of  experiments.  The  curves  B  (negative  selection)  and 
C  (positive  selection)  are  taken  from  the  first  year;  tliis 
was  done  because  the  two  following  years  brought  no 
further  progress  in  the  same  direction  in  spite  of  con- 
tinued selection.  The  experiments  extend  over  three 
generations ;  but  all  nine  curves  have  not  been  included 
since  this  would  have  rendered  the  figure  practically  un- 
intelligible. 

For  this  experiment,  seeds  of  the  laez'ifoIia-\mm\y 
(p.  273)  were  sown  in  1891  and  some  of  them  highly 
manured  with  horn-flour    (steamed  and  crushed   horns 

verted  into  percentages.  The  distance  of  the  ordinates  apart  is  7.5 
mm.    The  height  of  the  ordinates  is  1%  ^2  mm. 

A.   (123  plants)  The  original  curve  of  the  mean  fruit-length  after 

the  first  apphcation  of  nitrogenous  manure  in  1891. 
B  and  C.    The  result  of  manuring  the  mother-plant  in  1891. 
B  (78  plants)  The  next  generation  after  selection  of  short-fruited 
seed-parents.     The  curve  has  nevertheless  shifted  distinctly  to 
the  right.     1892. 

C.  (147  plants)   The  same  generation  as  B.  but  after  selection  c^f 

long-fruited   secdparents ;   the  curve  has  only  shifted  a   little 
more  than  B.    1892. 

D.  After  three  years  of  cultivating  the  seedlings  in  pots.  i.  e..  by 

the  most  effective  form  of  nutrition,  but  without  selection.  The 
curve  has  shifted  to  the  right  far  more  than  C".  1894  (88  plants). 


538  Length  of  the  Fruit  in  Oenothera  Larnarckiana. 

and  hoofs).  One  plant  with  very  long  fruits  and  two 
with  very  small  fruits  were  chosen  from  the  harvest, 
after  its  curve  (Fig.  116  A)  had  been  determined.  Their 
seeds  were  sown  separately  in  1892  and  moderately  ma- 
nured; the  curves  of  their  offspring  were  determined. 

The  result  was,  as  Fig.  116  shows,  that  the  length 
of  the  fruit  had  increased  in  both  cases.  We  see  that 
this  occurred  in  spite  of  the  choice  of  short-fruited  seed- 
parents  in  one-half  of  the  experiment.  The  effect  of 
manure  therefore  exceeded  that  of  selection  (Fig.  116 
A,  B,  and  C). 


HARVEST  OF   1891. 


MEAN  LENGTH 
IN  MM 

OF  FRUIT 

• 

NUMBER  OF  PLANTS 

WITH 

WITHOUT 

HORN-MANURE 

HORN-MANURE 

20 

1 

0 

21 

4 

0 

22 

7 

0 

23 

11 

5 

24 

21 

5 

25 

25 

10 

26 

20 

8 

27 

14 

10 

28 

10 

11 

29 

3 

4 

30 

4 

5 

31 

1 

4 

32 

1 

3 

33 

1 

4 

34 

0 

2 

Totals 

123 

71 

To  go  into  the  details  of  the  experiment :  it  must  be 
related  that  the  family  in  question  (1887-1890)  was 
grown  in  very  rich  soil  but  without  manure.     I  selected 


The  Operation  of  Nutrition  and  Selection.      539 

at  random  two  samples  of  seed,  each  of  wliich  liad  been 
well  mixed,  from  those  harvested  in  1890.  One  was 
sown  on  two  beds  of  about  2  square  meters  each ;  which 
had  received  a  dressing  composed  of  5  kilos  of  horn- 
flour,  and  10  kilos  of  this  manure  per  square  meter 
respectively.  This  culture  gave  123  healthy  plants  with 
ripe  fruits.  The  greater  part  of  the  seed  was  sown  on 
five  beds,  of  2  square  meters  each,  some  of  which  re- 
ceived no  manure  at  all,  whilst  others  were  given  %  to 
2%  kilos  of  ordinary  guano  per  square  meter.  Of  this 
crop  14-15  plants  were  chosen  at  random  from  each  bed 
and  employed  for  determining  the  second  curve. 

The  total  length  of  the  five  lower  fruits  was  meas- 
ured in  millimeters  (see  p.  532)  and  the  mean  length  of 
fruit  calculated  from  this. 

In  this  way  I  obtained  the  data  in  the  table  on  p.  538. 

The  following  figures  can  be  calculated  from  the 
first  generation  of  this  experiment,  raised  from  the  same 
lot  of  seeds : 

Qt  M  Q, 

With  horn  meal  1.3  25.2  1.5 

Without  horn  meal  1.9  27.2  2.4 

Hilversum  1.9  24.1  2.0 

In  the  third  row  I  have  written  the  corresponding 
values  for  O.  Lamarckiana  (1893),  for  the  sake  of  com- 
parison (see  pp.  530,  531  and  Fig.  115). 

The  cultivated  plants  have,  it  will  be  seen,  a  slight 
advantage  over  the  wild  ones,  which  is  smaller  in  the 
case  of  the  plants  which  had  horn-flour  than  in  those  in 
the  control  experiment.  The  horn-flour  culture  shows  a 
slight  decrease  in  the  amplitude  of  variation;  the  control 
experiment  a  trifling  increase. 

The  horn-flour  culture  was  the  only  one  which  was 


540  Length  of  the  Fruit  m  Oenothera  Lamarckiana. 

continued.  Three  individuals  from  it  were  chosen  as 
seed-parents;  the  mean  lengths  of  their  five  lowest  fruits 
measured  as  above  were  20.6,  20.6  and  32.6.  For  the 
sake  of  greater  certainty  I  also  measured  all  the  ripe 
fruits  on  these  stems  (27-33  fruits  each)  and  found  the 
mean  values  for  the  plants  to  be  19.0,  19.2  and  31.3. 
The  seed  of  the  single  long-fruited  stem  was  sufficient 
for  the  culture  of  1892;  but  I  had  to  take  two  of  the 
short-fruited  ones  to  get  a  sufficient  quantity  of  seed. 


HARVEST   OF    1892. 


MEAN  FRUIT  LENGTH 

NUMBER  OF  PLANTS 

IN  MM. 

K 

L 

23 

2 

0 

24 

2 

0 

25 

4 

0 

26 

5 

5 

27 

7 

5 

28 

12 

4 

29 

5 

8 

30 

5 

10 

31 

5 

17 

32 

12 

13 

33 

6 

13 

34 

6 

16 

35 

5 

16 

36 

2 

13 

37 

0 

5 

38 

0 

10 

39 

0 

6 

40 

0 

1 

41 

0 

2 

42 

0 

0 

43 

0 

3 

Totals 

78 

147 

In  1892  I  set  apart  a  bed  of  4  square  meters  for  each 


The  Operation  of  Nutrition  and  Selection.       541 

of  these  two  cultures:  it  was  dressed  with  Y:\  of  a  kilo 
of  dried  cow  manure  and  %  of  a  kilo  of  steamed  horn- 
flour  per  square  meter.  This  has  proved  the  most  satis- 
factory manure  I  have  tried:  plants  do  not  react,  in  the 
long  run,  to  larger  quantities. 

Otherwise  the  treatment  of  the  plants  was  the  same 
as  in  the  former  year;  they  grew  healthily;  tliere  were 
147  individuals  from  the  long-fruited  parentage,  and 
78  from  the  short-fruited.  The  fruit  lengths  were  deter- 
mined in  the  usual  way ;  and  the  numher  of  plants  which 
exhibited  the  various  fruit-lengths  are  given  in  the  table 
on  page  540,  in  which  K  signifies  the  offspring  of  short- 
fruited  and  L  that  of  long-fruited  parents. 

From  the  table  on  page  540  together  with  result  of 
the  sowing  of  1891  the  following  values  can  be  calculated  : 
under  S  are  given  the  fruit  lengths  of  the  seed  parents. 

S         Q,         M        Q^ 

Harvest  of  1891  —         1.3       25.2        1.5  (Fig.  116^) 

1892.  Short  fruited  culture       20.6       2.5       29.9       2.6  (Fig.  116  ^) 
1892.  Long  fruited  culture       32.6       2.6       33.4       2.4  (Fig.  116  C) 

and  further: 

MINIMUM  MAXIMUM 

Harvest  of  1891  20  mm.  33  mm. 

1892.  Short  fruited  culture  23  mm.  36  mm. 

1892.  Long  fruited  culture  26  mm.  43  mm. 

We  find  therefore  that  the  mean  fruit-length  has  in- 
creased considerably  in  both  cultures  of  1892,  and  that 
this  increase  has  been  more  considerable  when  long- 
fruited  seed-parents  have  been  chosen  than  when  short- 
fruited  ones  have.  The  same  is  true  of  the  extremes 
of  the  crops :  fruits  as  small  as  those  which  occurred  in 
1891  did  not  occur  in  the  cultures  of  1892:  on  the  otlicr 
hand  the  size  of  the  longest  fruits  increased  consider- 


542  Length  of  the  Fruit  in  Oenothera  Lainarckiana. 

ably  (the  maximum  increase  being  almost  a  third  of  the 
original  length). 

For  the  sake  of  further  discussion,  we  may  sum  up 
this  result  briefly  in  two  theses : 

1.  In  both  cases  the  length  of  the  fruit  increased. 

2.  With  the  selection  of  a  long-fruited  seed-parent 
this  increase  was  considerably  greater  than  when 
a  short-fruited  one  was  selected. 

It  is  evident  that  the  latter  fact  is  simply  the  result 
of  selection.    All  the  other  conditions  of  the  experiment- 
were  exactly  the  same,  and  the  difference  in  the  results 
is  exactly  what  one  would  expect  as  the  result  of  selec- 
tion.    We  need  not  therefore  enter  further  into  it. 

But  it  is  a  very  different  matter  that  the  length  of 
the  fruit  increased  in  both  cultures  and  especially  that 
this  happened  in  the  case  of  the  choice  of  short-fruited 
seed-parents.  This  cannot  have  been  the  result  of  selec- 
tion, and  the  only  other  possible  cause  can  have  been  the 
heavy  manuring  of  the  parent-plant  with  horn-flour. 

In  the  long-fruited  culture  the  mean  fruit-length 
(33.4  mm.)  was  larger  than  the  corresponding  value  in 
the  seed-parent  (32.6  mm.).  The  known  principles  of 
selection,  and  particularly  Galton's  researches  on  re- 
gression, make  the  interpretation  of  this  result  as  the 
effect  of  selection,  impossible.  Selection  would,  of  course, 
effect  an  increase  in  the  length  of  the  fruit,  but  the  new 
value  would  have  to  lie  between  the  original  mean  and 
the  fruit-length  of  the  seed-parent.  Here  however  it 
was  greater  than  that  of  the  seed-parent,  and  this  can 
only  be  ascribed  to  the  heavy  manuring  of  the  parent- 
plants.^ 

^  I  have  often  observed  this  effect  of  the  manuring  of  the  parent- 
plants  in  cuhures  with  other  species,  for  example  in  Ranunculus 
bulbosits  in  pleiopetaly.     See  the  second  volume. 


The  Operation  of  Nutrition  and  Selection.      543 

Let  us  now  turn  to  the  amplitude  of  variation  (Q). 
This  was,  as  the  above  table  shows,  the  same  in  both 
cultures  in  1892  and  double  as  large  as  in  the  horn-flour 
culture  of  1891.  In  this  latter  it  was,  in  fact,  smaller 
than  in  the  ordinary  cultures  (p.  539).  The  amplitude 
of  fluctuation  is  well  known  to  be  brought  about  by  the 
multiformity  of  internal  and  external  conditions  which 
afifect  development,  and  it  is  obvious  that  heavy  manuring 
will  tend  to  level  these  differences  down.  We  shall  refer 
to  a  parallel  result  when  we  come  to  describe  the  contin- 
uation of  the  short-fruited  race. 

Finally,  it  will  be  seen  that  Q\  and  Qo  have  remained 
equal  to  one  another  and  therefore  that  the  curve,  in  spite 
of  the  shifting  of  its  apex,  has  remained  symmetrical. 

Regarded  from  the  methodological  point  of  view, 
this  experiment  contains  a  warning  to  keep  the  external 
conditions,  particularly  those  of  manuring,  as  constant 
as  possible;  and  not  to  be  too  ready  to  interpret  any 
changes  that  may  occur  as  the  effects  of  selection. 

As  already  stated  I  have  cultivated  the  two  races  for 
two  more  years  under  exactly  the  same  treatment  ( 1S^\>. 
1894).  The  long-fruited  race  underwent  no  further  im- 
provement; in  fact  they  deteriorated  a  little.  This  result 
is  an  illustration  of  Hallett's  principle  (see  ]).  ll(V), 
which  enabled  him  to  evolve  his  new  varieties  of  cereals. 
During  the  first  year  of  his  experiments  notable  progress 
was  made;  but  after  that,  further  selection  either  made 
ver}^  slight  further  progress,  or  only  served  to  fix  what 
had  already  been  attained. 

In  1891-1892  I  left  pollination  to  the  agency  of  in- 
sects, but  in  the  summer  of  1893  I  pollinated  the  fl<nvers 
artificially  after  having  excluded  the  visits  of  insects  by 
bags.     But  this  has  not  led,  so  far  as  I  have  observed. 


544  Length  of  the  Fruit  in  Oenothera  Lamarckiana. 

to  any  considerable  difference  in  the  results.  The  sig- 
nificance  of  free  crossing  by  insects  is  usually  very  much 
exaggerated.  The  pollination  of  the  evening  primrose 
is  chiefly  done  by  humble-bees;  although  Pliisia  gamma, 
Agrotis  segetum  and  allied  moths  participate  to  a  small 
extent  in  my  garden.  These  insects,  especially  the  humble- 
bees,  usually  visit  all  the  flowers  on  the  same  stem  one 
after  the  other,  so  that  there  is  a  great  amount  of  self- 
fertilization  taking  place. 

In  1892  I  placed  the  separate  cultures  at  some  dis- 
tance from  one  another,  and  separated  them  by  brush 
wood,  so  that  frequent  crossings  between  them  were 
practically  impossible.  Artificial  pollination  in  these  ex- 
periments has  the  great  disadvantage  that  one  has  to 
choose  the  seed-parents  whilst  they  are  in  flower,  that 
is  to  say,  a  long  time  before  the  full  development  of  their 
fruits ;  the  choice  is  therefore  not  nearly  as  free  as  when 
pollination  is  left  to  insects. 

The  following  description  of  my  experiments  shall 
be  condensed  as  much  as  possible.  I  shall  begin  with  the 
long-fruited  race. 

The  seed-parents  in  1892  were  two  plants  with  a 
mean  fruit-length  of  42.6  to  43.0  mm.  The  seed-parents 
in  1893  were  three  plants  whose  mean  fruit-lengths  w^ere 
37.0,  37.0  and  41.0.  In  the  first  year  therefore  there  was 
a  considerable  advance  on  the  fruit-length  of  the  plants 
chosen  in  1891  (32.6)  ;  in  the  second  year  however  a 
slight  retrogression  which  was  brought  about  by  the 
necessity,  referred  to  just  now,  of  carrying  out  the  se- 
lection before  the  fruits  were  ripe. 

The  crop  in  both  years  was  dealt  with  and  measured 
in  exactly  the  same  way  as  in  1892.     There  resulted  the 


The  Operation  of  Nutritiun  and  Selection.       545 

following  numbers  of  individuals  of  the  various  mean 
fruit-lengths  given  in  the  first  columns  Ijelovv. 


LONG-FRUITED  RACE  IN   THE' YEARS    1893   AND    IS^U. 


MEAN   FRUIT 

LENGTH 

NUMBER  OF  PLANTS 

IN  MM 

1893 

1894 

23 

0 

9 

24 

1 

3 

25 

3 

9 

26 

5 

2 

27 

7 

9 

28 

6 

8 

29 

15 

9 

30 

12 

8 

31 

15 

6 

32 

11 

11 

33 

14 

9 

34 

10 

14 

35 

10 

6 

36 

6 

5 

37 

5 

3 

38 

2 

1 

39 

0 

1 

40 

2 

1 

41 

1 

1 

Totals 

125 

101 

The  values  Q  and  M  calculated  from  the  above  tabic 
are  given  below;  together  with  the  corresponding  values 
for  the  ancestors,  of  1891  and  1892,  and  the  lengths  of 
the  fruits  of  the  individual  plants  which  furnislied  the 
seeds  (5*^  seed-parent).  There  stands  therefore  under 
vS'  in  each  row  the  length  of  the  fruit  of  the  seed-parent 
chosen  in  the  preceding  autumn ;  their  seeds  gave  rise 
to  the  crop  referred  to  in  the  same  line. 


546  Length  of  the  Fruit  in  Oenothera  Lamarckiana. 


5 

Q. 

M 

Q2 

Harvest  of  1891 

— 

1.3 

25.2 

1.5 

"  1892 

32.6 

2.6 

33.4 

2.4 

'•  1893 

42.6—43.0 

2.3 

31.4 

2.6 

"  1894 

37.0—41.0 

3.2 

31.6 

2.4 

The  mean  fruit-length  has  therefore,  in  spite  of  rigid 
selection  not  only  not  increased  but  actually  decreased. 
Selection  can  do  no  more  than,  to  use  Hallett's  expres- 
sion, fix  the  fruit-length  attained  by  high  nutrition :  and 
it  barely  manages  that. 

The  quartiles  have  remained  pretty  constant  since 
1892;  the  curve  has  remained  practically  symmetrical 
and  its  amplitude  has  neither  increased  nor  decreased 
much. 

The  increase  in  the  mean  fruit  length  was  effected 
(in  1892)  without  any  regression;  but  after  that  the 
selection  was  accompanied  by  a  heavy  regression;  that 
is  to  say,  the  value  of  M,  reached  in  the  years  1893  and 
1894,  fell  far  short  of  the  M  of  the  selected  seed-pa- 
rents   {S).  :1c         *         * 

We  now  come  to  the  continuation  of  the  short-fruited 
race  in  the  two  years  1893-1894. 

Like  the  long-fruited  culture,  this  was  continued  for 
two  more  years  under  normal  conditions  of  manuring 
and  by  selecting  seeds  from  very  short-fruited  plants, 
for  raising  the  next  generation.  In  §  3  it  was  shown 
that  short-fruited  plants  were  as  a  rule  ill-favored,  i.  e., 
poorly  nourished  ones.  In  this  way  selection  would 
very  soon  counteract  the  effect  of  the  heavy  manuring 
of  1891.  And  the  mean  fruit-length  has,  as  a  matter 
of  fact,  undergone  a  marked  diminution  in  these  two 
years,  whereas  the  amplitude  of  variation  has,  on  the 
other  hand,  increased  considerably. 


The  Operation  of  Nutrition  and  Selection.       547 


The  culture  extended  in  1893  over  four  and  in  1804 
over  six  square  meters,  manured  with  dried  cow  manure 
and  horn-flour  as  before.  Two  plants  with  mean  fruil- 
lengths  of  2Z.2  and  23.4  mm.  were  chosen  to  supply  the 

SHORT-FRUITED  RACE  IN  THE  YEARS  1893  AND    1804. 


MEAN  FRUIT  LENGTH 

NUMBER  OF  PLANTS 

IN  MM. 

1893 

1894 

16 

1 

0 

17 

1 

1 

18 

4 

2 

19 

4 

3 

20 

2 

11 

21 

9 

12 

22 

13 

12 

23 

8 

11 

24 

7 

10 

25 

11 

5 

26 

9 

8 

27 

15 

4 

28 

9 

2 

29 

9 

8 

30 

7 

4 

31 

10 

7 

32 

13 

6 

33 

1 

4 

34 

2 

3 

35 

0 

0 

36 

2 

4 

37 

1 

1 

38 

0 

0 

39 

1 

0 

Totals 

139 

118 

1893  crop.  In  this  year  the  short-fruited  plants  afforded 
so  little  seed,  partly  on  account  of  the  small  number  of 
artificially  fertilized  flowers,  that  seed  of  six  plants  had 
to  be  harvested  to  provide  a  sufficient  quantity  (8.6  ccm). 


548  Length  of  the  Fruit  in  Oenothera  Lamarckiana. 

The  mean  fruit-lengths  for  these  six  seed-parents  were 
15.6,,  17.0,  18.2,  19.2,  20.2  and  21.4;  the  average  of 
which  is  18.6  mm. 

The  fruit-length  of  the  seed-parent  chosen  in  1891 
was  20.6;  from  which  we  see  that  the  above  figures  are 
nothing  more  than  fluctuations  round  a  similar  mean. 

The  harvest  was  again  treated  in  the  same  way ;  the 
mean  fruit-length  was  determined  for  each  plant  from  the 
total  length  of  the  lowest  five  good  fruits :  in  the  table 
on  page  547  are  given  the  numbers  of  individuals  ex- 
hibiting the  various  lengths  written  in  the  column  to 
the  left. 

Here  are  the  values  calculated  from  this  table ;  to- 
gether with  those  of  their  ancestors  and  of  the  seed- 
parents  {S)  chosen  each  year. 


5 

Qx 

M 

Qz 

Harvest  of  1891 

1.3 

25.2 

1.5 

"  1892 

20.6 

2.5 

29.9 

2.6 

"  1893 

23.2—23.4 

3.9 

26.5 

3.3 

"  1894 

15.6—21.4 

2.7 

24.2 

5.2 

These  figures  show  that  the  mean  fruit-length  de- 
creased about  as  much,  as  a  result  of  thrice  repeated 
selection,  as  they  had  increased  in  1892  as  the  result  of 
the  heavy  manuring  of  1891.  Regression  took  place,  as 
was  to  be  expected,  in  the  two  years  covered  by  the  ex- 
periment. The  amplitude  of  variation  exhibited  a  marked 
increase  in  this  experiment;  the  external  and  internal 
causes  affecting  the  growth  of  a  plant  are  obviously 
multiplied  by  the  choice  of  ill-favored  individuals  under 
favorable  conditions  of  cultivation.  In  other  words : 
selection  and  cultivation  exert  their  influence  in  opposite 
directions  in  this  case,  whereas  in  the  long-fruited  race 
they  exerted  it  in  the  same  direction;  hence  the  ampli- 


The  Operation  of  Nutrition  and  Selection.      540 

tude  of  variation  Iq  =  ^^^\  increases  in  this  case  but 

not  in  the  former. 

In  connection  with  this  result,  there  are  two  further 
points  relating  to  the  selection  of  continuous  varia- 
tions. 

In  the  first  place  both  agricultural  and  horticultural 
selection  is  usually  accompanied  with  moderate  manur- 
ing, and  the  most  desirable  individuals  are  usually  found 
amongst  the  strongest  ones.  Inasmuch  as  we  have  here 
a  contrast  similar,  though  working  in  the  reverse  wav, 
to  that  which  obtains  in  our  experiments,  we  may  expect 
an  increase  in  the  amplitude  of  variation  as  a  result  of 
this  contrast. 

In  the  second  place  if  I  had  mixed  the  two  races  in 
1894,  or  if  I  count  the  figures  in  the  tables  on  pp.  545 
and  547  together  and  calculate  Qiy  M  and  Qo,  from  the 
whole  lot  I  get   (for  118+101=219  plants): 


Qi  ^1  Qz  Q= 


Qr+Q^ 


2 
1894  5-0  28.6  3.8  4.4 

whereas  Q  for  the  short-fruited  race  alone  was 

2-7  +  5.2 
2       ~ 

That  is  to  say,  the  amplitude  of  variation  is  so  much  in- 
creased by  the  opposite  action  of  nutrition  and  selection, 
that  it  can  only  very  slightly  increase  further  by  lump- 
ing the  extreme  variants  in  both  directions  together.  In 
other  words  Q  (in  the  case  before  us)  is  increased  far 
more  by  the  changing  conditions  of  nutrition  in  the  in- 
dividual plants  on  the  same  bed  than  it  can  be  by  selection 
in  two  opposite  directions. 

Summary.     I  append  the  values  for  0\,  M  and  0- 


550  Length  of  the  Fruit  in  Oenothera  Lamar ckiana. 

derived  from  the  aoove  experiments,  collected  in  a  single 
table.     The  numbers  signify  millimeters  as  before. 

FRUIT  LENGTH  OF  OENOTHERA  LAMARCKIANA. 

Date             5  Qi  ^  Qz 

Original  form,  Hilversum       1893             —  1.9  24.1  2.0 

"       culture             1891             —  1.3  25.2  1.5 

Long  fruited  race                     1892            32.6  2.6  33.4  2.4 

1893  42.6—43.0  2.3  31.4  2.6 

1894  37.0—41.0  3.2  31.6  2.4 
Short  fruited  race                      1892            20.6  2.5  29.9  2.6 

1893  23.2—23.4      3.9      26.5      3.3 

1894  15.6—21.4      2.7      24.2      5.2 

^  I  regard  the  following  generalizations  as  the  most  im- 

portant results  of  these  experiments,  combined  with  the 
results  detailed  in  the  next  section  (Fig.  116  D)  : 

1.  The  variation  of  the  length  of  the  fruit  follows 
the  Ouetelet-Galton  law  (Fig.  116  A-D).  Each  curve 
is  determined  by  three  values.  The  median,  M,  or  the 
mean  value,  and  the  two  quartiles  Qi  and  Q2  within 
which  fall  half  of  the  deviations  from  the  mean. 

2.  The  mean  fruit-length  is  much  influenced  by  nu- 
trition as  well  as  by  selection,  and  more  by  a  single 
manuring  of  the  parent-plant  than  by  a  once  or  twice 
or  even  thrice  repeated  selection  of  long-fruited  plants 
as  seed-parents  (long-fruited  race  1891-1894).  It  is 
influenced  even  more  by  a  few  years  of  cultivating  the 
seedlings  in  pots,  and  the  addition  of  much  manure  to 
the  pots  of  the  seedlings  (pot-culture  without  selection 
1892-1894,  §5). 

3.  The  amplitude  of  variation  f  g  =  ^^"*"^|  increases 

only  slightly,  so  long  as  nutrition  and  selection  work 
in  the  same  direction.  But  as  soon  as  they  work  in  oppo- 
site directions  the  multiformity  of  affecting  causes  in- 


The  Shifting  of  the  Curves  of  Variability.       551 

creases,   and   the   amplitude   of   variation   increases   too 
(short-fruited  race  1891-1894). 

4.  The  variability-curves  remain  ahncjst  symmetrical 
(0i=Q2)  although  their  apices  are  considerably  shifted 
to  one  side.  The  deviations  from  this  symmetrical  form 
almost  all  lie  within  the  limit  of  ordinary  errors  of  obser- 
vation. 


§  5.    THE  SHIFTING  OF  THE  CURVES  OF  VARIABILITY 

BY  NUTRITION. 

Oenothera  Lamarckiana,  and  other  plants  as  well, 
may  be  stimulated  to  a  much  swifter  and  more  vigorous 
growth  by  planting  the  seeds  in  pans  and  picking  out 
the  young  seedlings  soon  after  the  unfolding  of  the 
cotyledons  into  fairly  large  pots  filled  with  heavily  ma- 
nured garden  soil.  One  would  expect  that,  by  continuing 
this  process  for  a  few  generations,  it  would  be  possible 
to  increase  the  mean  fruit-length  very  considerably,  in 
accordance  with  the  principle  of  nutrition  of  the  parent- 
plant. 

The  experiment  to  be  described  fulfils  this  expecta- 
tion; the  increase  made  in  three  years  (1892-1894)  far 
exceeds  that  made  in  the  selection  experiments  already 
described,  in  which  the  seed  was  sown  in  the  garden 
(Fig.  116). 

Let  us  give  a  description  of  this  experiment  year  by 
year.  It  began  in  the  spring  of  1892  with  the  seeds  (if 
the  species  Oenothera  ruhrinervis  (p.  273)  which  arose 
in  my  experimental  garden  in  1889:  the  length  nf  the 
fruit  in  this  species  is  the  same  as  in  O.  Lauiarckiaua 
(Fig.  99,  p.  446). 

In  1890  the  seeds  were  harvested  from  a  number  of 


552  Length  of  the  Fruit  in  Oenothera  Laniarckiana. 

plants  without  any  attention  being  paid  to  their  fruit- 
length;  in  1891  however  the  plants  with  short  fruits 
were  weeded  out  before  they  ripened  their  seed.  The 
seeds  of  the  remainder  were  mixed  and  sown  in  wooden 
boxes,  in  February,  in  the  greenhouse  belonging  to  my 
laboratory.  As  soon  as  the  cotyledons  were  fully  un- 
folded a  number  were  planted  out  singly  in  pots  of  9-10 
centimeters  in  diameter  without  any  regard  to  differ- 
ences in  development  (which  as  a  matter  of  fact  at  this 
stage  are  scarcely  appreciable).  The  soil  was  a  good  leaf 
mould,  to  every  litre  of  which  was  added  10  grammes 
of  dry  powdered  cow  manure  and  10  grammes  of  horn 
flour,  a  very  strong  dressing  which  I  have  used  with  the 
best  results  for  producing  contortions,  fasciations  and 
other  structural  abnormalities.^  The  young  plants  were 
at  first  kept  under  glass  until  the  rosettes  were  very 
strong  and  had  begun  to  develop  a  stem.  At  the  end 
of  May  they  were  planted  out  in  my  experimental  garden 
in  a  bed  far  removed  from  the  other  cultures.  As  in 
the  latter  the  plants  were  deprived  of  all  their  lateral 
branches,  so  that  they  flowered  only  on  the  main  stem. 

Thanks,  doubtless,  to  the  early  sowing  and  to  accel- 
erated early  growth  this  culture  flowered  some  weeks 
earlier  than  the  others;  they  also  ripened  their  fruits 
considerably  earlier.  I  had  altogether  22  plants  whose 
seeds  were  harvested  separately.  Of  these  I  chose  five 
for  next  year's  sowing  after  harvesting  time  was  well 
past,  and  the  fruits  were  no  longer  at  hand.  In  this  way 
no  regard  could  be  paid  to  the  fruit-length  of  the  seed- 
parents  which  had  not  even  been  measured. 

Next  year  (1893)  the  seed  was  sown  in  the  middle 

^  Eine  Methode  Zwangsdrehungen  aufstisucken;  Ber.  d.  d.  bot. 
Gesellsch.,  Bd.  XII,  1894,  P-  25. 


The  Shifting  of  the  Curves  of  Variabilitx.       553 

of  March  in  exactly  the  same  manner  as  described  above ; 
as  soon  as  the  seedhngs  had  fully  unfolded  their  cotyle- 
dons they  were  planted  out  into  the  same  comi)ost  as  in 
1892,  and  treated  in  the  same  way  subsequently.  Towards 


CULTURE    OF    THE    SEEDLINGS    IN    POTS ;    OENOTHERA 

RUBRINERVIS. 


MEAN  FRUIT  LENGTH 

NUMBER  OF  PLANTS 

IN  MM. 

1893 

1894 

24 

2 

0 

25 

2 

0 

26 

2 

0 

27 

4 

0 

28 

5 

1 

29 

5 

1 

30 

7 

1 

31 

10 

3 

32 

15 

2 

33 

7 

5 

34 

2 

2 

35 

7 

5 

36 

1 

4 

37 

0 

10 

38 

0 

10 

39 

0 

16 

40 

0 

7 

41 

0 

9 

42 

0 

7 

43 

0 

1 

44 

0 

4 

Totals 

69 

88 

From  which  the  following  vahies  have  been  calculated  for  Qi, 
M,  Q2: 


Pot-culture 

Year 

Qx 

M 

£?= 

Min. 

Max 

2nd  generation 

1893 

2.2 

31.2 

1.3 

24 

3G 

3rd  generation 

1894 

2.5 

38.3 

2.2 

28 

44 

554  Length  of  the  Fruit  in  Oenothera  Lamarckiana. 

the  end  of  September  I  had  69  plants  with  ripe  fruits. 
Their  lengths  were  measured  in  the  usual  way  on  the 
lowest  five  good  fruits;  and  the  figures  thus  obtained 
are  given  in  the  1893  column  of  the  table  on  page  553. 

I  now  had  to  make  a  sowing  without  reference  to 
fruit-length.  I  sowed  the  seeds  of  nine  plants  whose 
mean  fruit-lengths  were  24.2,  26.2,  26.8,  27.0,  27.4,  29.0, 
32.4,  34.  6,  35.2  mm.  The  mean  of  them  was  therefore 
28.1  mm.,  which  is  below  the  median  of  the  whole  1893 
crop  (see  below)  whilst  only  the  last  two  figures  lie 
above  the  upper  quartile. 

Sowing,  pricking  out,  manuring  and  cultivation  were 
the  same  in  1894  as  in  the  previous  years.  At  harvest 
time  I  had  88  plants  with  ripe  fruits;  from  7  to  19  from 
each  parent  plant,  with  the  exception  of  the  three  parents 
with  the  longest  fruits  which  gave  rise  to  only  4,  5  and 
6  plants  respectively,  whereby  their  effect  on  the  curves 
was  diminished  considerably.  The  measurements  of  the 
mean  fruit-lengths  were  again  made  in  the  same  way. 

The  numbers  of  individuals  in  the  various  groups  of 
fruit-lengths  are  given  in  the  table  on  page  553. 

The  mean  fruit-length  has,  it  will  be  seen,  increased 
considerably :  this  is  also  well  seen  by  looking  at  curve 
D  in  Fig.  116  and  comparing  it  with  the  corresponding 
curve  for  0.  Lamarckiana,  a  perfectly  legitimate  pro- 
ceeding inasmuch  as  both  species  exhibit  the  same  length 
of  fruit  under  similar  circumstances.  The  greatest  length 
attained  in  the  experiments  with  0.  Lamarckiana  was 
33.4  which  was  reached  by  manuring  the  parent  plants 
sown  in  the  garden,  and  by  the  selection  of  the  longest 
fruited  plant  as  seed  parent. 

This  enormous  increase  holds  good  not  only  for  the 
mean   but   for  all   individuals.      For  the   amplitude   of 


The  Shifting  of  the  Curves  of  Variability.       555 

variation  (Qi,  Q2)  has  not  increased  very  much,  and 
is  in  fact  a  httle  less  than  in  the  experiments  with  selec- 
tion. Accordingly,  the  minimum  and  maximum  have 
been  shifted  in  a  most  striking  way  in  the  same  direc- 
tion: small  fruits  are  absent  after  three  years  of  pot- 
culture  of  the  seedlings,  whilst  the  longest  fruits  have 
increased  greatly  in  length. 


III.  CURVES  OF  RAY-FLORETS  OF  THE  COM- 

POSITAE  AND  OF  RAYS  OF  UMBELS 

IN  THE  UMBELLIFERAE. 

§  6.    THE  OBLITERATION   OF  THE  EFFECT   OF   SELEC- 
TION BY  NUTRITION. 

We  must  now  inquire  whether  the  conclusions  arrived 
at  by  our  study  of  the  fruit-lengths  of  Oenothera  La- 
mar ckiana  apply  to  other  species  and  other  characters  as 
well.  I  propose  to  confine  myself  to  a  single  case — the 
operation  of  nutrition  and  selection  in  opposite  direc- 
tions, a  case  exactl}^  parallel  to  that  studied  in  the  short- 
fruited  race  of  Oenothera  Lamarckiana.  The  effect  of 
selection  is  pretty  accurately  known ;  so  that  the  separate 
effects  of  selection  and  nutrition  can  be  directly  inferred 
from  the  result  of  such  an  experiment.  It  is  a  question 
of  the  effect  of  selection  in  a  minus  direction ;  of  how  a 
character  will  behave  when  we  try  at  the  same  time  to 
impair  it  by  selection,  and  improve  it  by  nutrition. 

To  make  the  significance  of  the  point  at  issue  still 
clearer  I  will  give  a  short  summary  of  the  results  de- 
tailed in  this  and  the  two  following  sections.  They 
show  that  under  the  above  conditions  of  experiment  the 
effect  of  nutrition  exceeded  that  of  selection  in  Anethiim 
graved  ens  (§6),  that  in  other  cases  both  had  about  the 
same  effect,  as  in  Chrysanthemum  segetiim.  Coreopsis 
tinctoria,  and  Bidens  grandi flora  (§7),  and  finally  that 


Effect  of  Selection  Obliterated  by  Nutrition. 


D.-1/ 


in  Coriandriim  sativum  and  Madia  elcgans  selection  had 
decidedly  a  greater  effect  (§8).  Thus  we  see  that  in 
such  experiments  selection  and  nutrition  are  factors  of 
the  same  order,  and  therefore  that,  in  hreeding  experi- 
ments on  the  effect  of  one  of  these  factors,  the  first  con- 
dition, although  it  is  often  extremely  difficult  to  fulfil, 
is  that  the  other  factor  should  be  kept  perfectly  constant. 

The  characters  whose  variation  I  investigated  were 
the  number  of  rays  in  the  umbels  of  Ancthiim  and  Co- 
riandrum,  the  number  of  ray-florets  in  the  heads  of 
Chrysanthemum,  Coreopsis,  Bidens  and  Madia.  The 
numbers  of  these  vary  pretty  considerably,  and  afford 
beautiful  illustrations  of  Ouetelet's  law,^  as  will  be  seen 
at  the  first  glance  at  our  figures.  For  the  construction 
of  the  curves,  the  numbers  of  rays  on  the  terminal  umbel 
or  head  of  the  main  stem  was  taken  as  a  measure  of  this 
character  in  the  individual  in  question;  no  attention  was 
paid  to  the  lateral  umbels  and  secondary  heads.  Seed 
was  gathered  without  regard  to  the  qualities  of  these 
lateral  umbels  and  heads ;  except  that  those  plants  whose 
secondary  or  tertiary  umbels  or  heads  remained  too  much 
behind  the  primary  one,  were  always  the  first  to  be  rooted 
out. 

The  experiments  began  in  the  spring  of  1892.  The 
seed  for  sowing  was  obtained  either  from  nursery-men 
or  from  botanical  gardens  {Chrysanthemum).  It  must 
therefore  have  been  obtained  from  moderatel}'  manured 
cultures,  and  was  sown  by  me  in  rich  but  not  too  heavily 
manured  soil,  in  the  open.  During  the  three  years  of  the 
experiment  the  manuring  and  other  treatment  was  uni- 
form.    The  manure  was  the  same  as  that  which   was 

'^Ber.  d.  d.  hot.  Ges.,  Bd.  XII,  1894,  p.  200.  {Coreopsis  and  Anc- 
thum). 


558        Curves  of  Compositae  and  Umbclli ferae. 

given  to  the  Oenotheras  in  the  same  year,  that  is,  %  Kilo 
of  dried  cow  manure  and  %  Kilo  of  steamed  horn  flour, 
per  square  meter.  This  mixture  was  spread  over  the 
beds  as  uniformly  as  possible  a  few  days  before  sowing 
and  well  dug  in.  I  considered  the  much  richer  horn  flour 
manure  which  I  had  given  to  the  Oenotheras  in  1891  as 
superfluous  for  this  experiment. 

This  constant  high  nutrition  supplied  during  the  three 
years  of  the  experiment  would  lead  us  to  expect  a  pro- 
gression of  M ;  and  the  selection  a  retrogression  of  M. 

I  chose  as  seed-parents  the  plants  with  the  smallest 
number  of  ,rays  in  the  primary  umbel  or  head.  In  the 
Umbelliferae  this  could  be  counted  before  the  plants 
flowered  and,  inasmuch  as  the  remaining  plants  were 
pulled  up  before  the  selected  seed-parents  began  to 
flower,  crossing  could  be  prevented.  The  composites 
on  the  same  bed  did  not  flower  all  at  once;  each  plant 
was  recorded  as  soon  as  its  rays  could  be  counted  and 
pulled  up  if  it  was  not  wanted  as  a  seed-parent.  The 
possibility  of  crossing  was  thus  diminished  as  much  as 
possible ;  in  addition  to  this,  the  seed-parents  were,  when- 
ever possible,  deprived  of  all  the  heads  that  were  over 
or  still  flowering,  as  soon  as  the  selection  was  finished, 
in  order  to  get  only  purely  fertilized  seeds  for  sowing. 
Such  cultures  are  often  threatened  by  numerous  pesti- 
lences and  misfortunes  which  only  too  often  sweep  away 
every  single  seed-parent,  after  the  others  have  been 
pulled  up.  For  example  in  1894  the  experiment  with 
Coriandrum  sativum  was  thus  brought  to  an  untimely 
end.  Occurrences  of  this  kind  led  me  to  spare  a  larger 
series  of  seed-parents  than  would  otherwise  have  been 
necessary.  Occasional  cross-fertilization  could,  of  course, 
take  place  among  them  as  a  result  of  this.     From  among 


Effect  of  Selection  Obliterated  by  Nutrition.     559 

them  I  chose,  after  harvest  was  over,  as  many  of  the 
best  as  were  sufficient  to  supply  the  seed  for  the  next 
sowing. 

From  this  summary  of  the  general  arrangement  of  the 
experiment,  let  us  proceed  to  the  description  of  our  se- 
lection culture  with  the  dill  {Anethiuii  graveolcns,  V\g. 
117). 

For  this  experiment  seeds  were  bought  from  the 
trade  and  sown  in  1892  over  1  square  meter,  llie  cnjp 
consisted  at  harvest  time  of  56  plants.  The  number  of 
rays  in  the  umbels  varied  between  12  and  38  and,  as  a 
rule,  in  direct  proportion  with  the  vigor  of  the  ])lant. 
Six  plants  with  12-16  rays  in  the  terminal  umbel  were 
chosen  as  seed-parents  and  their  seeds  sown  in  1893  over 
an  area  of  8  square  meters.  The  number  of  plants  when  I 
came  to  select  them  was  541,  and  as  was  to  be  expected 
in  so  much  larger  a  number  the  minimum  and  maximum 
were  further  apart;  9  and  43.  Five  plants  with  10-13 
rays  in  the  terminal  umbel,  were  chosen  as  seed  parents 
which  constituted  a  notable  advance  in  the  minus  direc- 
tion, as  compared  with  1892. 

In  1894  the  culture  extended  over  6  square  meters 
and  the  number  of  plants  when  I  came  to  select  them  was 
162. 

The  table  on  page  560  gives,  for  each  of  the  three 
crops,  the  number  of  individuals  whose  terminal  umbel 
had  the  number  of  rays  given  in  the  first  column. 

The  figures  (p.  560)  show  that,  in  spite  of  the  fact 
that  each  year  plants  were  chosen  with  a  markedly  smaller 
number  of  rays  than  the  mean  of  the  group  from  which 
they  were  chosen,  the  mean  number  of  rays  clearly  in- 
creased during  the  experiment.  The  better  manuring  had 
therefore  more  effect  than  the  selection  of  weak  plants. 


560        Curves  of  Compositae  and  Umhelliferae. 


ANETHUM  GRAVEOLENS. 


NUMBER  OF  RAYS 


9 

10 

11 

12 
13 
14 
15 
16 
17 
18 
19 
20 
21 
22 
23 
24 
25 
26 
27 
28 
29 
30 
31 
32 
33 
34 
35 
36 
37 
38 
39 
40 
41 
42 
43 


NUMBER  OF  PLANTS 


1892 

1893 

1894 

0 

4 

0 

0 

4 

0 

0 

4 

0 

1 

6 

1 

1 

18 

3 

0 

15 

1 

3 

23 

5 

7 

29 

4 

6 

26 

3 

12 

42 

9 

6 

32 

6 

3 

40 

6 

1 

38 

11 

5 

43 

10 

3 

44 

9 

0 

33 

7 

1 

24 

9 

1 

25 

15 

0 

25 

10 

1 

12 

7 

1 

11 

5 

0 

4 

8 

1 

5 

6 

1 

8 

6 

0 

4 

4 

1 

7 

3 

0 

5 

5 

0 

4 

1 

0 

1 

4 

1 

0 

0 

0 

2 

4 

0 

0 

0 

0 

1 

0 

0 

1 

0 

0 

1 

0 

Effect  of  Selection  Obliterated  by  Nutrition.     561 


The  following  values  have  been  calculated  from  this  table : 


Year    Seed  parent     Qi 


1892 

1893 

1894 

Increase  1892—1893 

1893—1894 


12—16 
10—13 


1.5 
3.6 
4.5 


Af 

18.3 
21.2 
25.2 


3.6 
3.5 
4.4 


M 

0.14 
0.17 
0.18 


4-2.1        4-2.9        -0.1 
4-0.9        4-4.0        +0.9 


The  amplitude  of  variation  also  increased  exactly  as  it 
did  in  the  short-fruited  race  of  Oenothera  Lamarckiana 
under  similar  conditions. 

The  value   0/M  renders  possible  a  comparison  be- 
tween the  amplitude  of  variation  in  this  case  and  in  0. 


/ 

1 

/ 

Aj 

189 

r\ 

Y 

^.  7 

> 

1       ^ 

'\ 

y 

\   \ 

,iS< 

}S 

y 
y 

/,^' 

\ 

/ 

\ 

\ 

_^ 

y^-^ 

\ 

^ 

^^^ 

..J-- 

^ 

__.- 

'^-^''^ir^ 

^y—^:. 

J,i      66      3S      !iO      U2 

Fig.  117.  Anethnm  gravcolcns.  Curves  of  the  rays  of  the 
temiinal  umbel.  The  numbers  under  the  abscissae  refer 
to  the  rays  of  the  primary  umbel.  In  accordance  with 
the  rule  discussed  on  page  527  the  number  of  ordinates 
is  half  the  number  of  groups  in  the  table.  The  figure  8 
therefore  means  eight  and  nine  rays  and  so  forth. 

A.  (56  plants)  Curve  of  1892,  irregular  on  account  of 
the  small  number  of  individuals.  It  is  also  asymmet- 
rical being  drawn  out  more  to  the  right. 

B.  (518  plants)  Curve  of  the  following  generation 
1893.  As  a  result  of  nutrition  and  selection  it  has  be- 
come nearly  symmetrical. 

Lamarckiana,  where  it  was  0.08  (p.  531).  The  number 
of  umbel-rays  is  therefore,  when  measured  in  this  way. 
twice  as  variable  as  the  fruit-length  in  Oenothera. 

The  asymmetrical  curve  of  the  year  1892  ((?2>(?i) 


562        Curves  of  Compositae  and  Umhelliferae. 

became  symmetrical  in  the  two  following  years  as  can  be 
clearly  seen  by  comparing  curve  A  (1892)  and  B  (1893) 
in  Fig.  117. 

§  7.    EQUILIBRIUM  BETWEEN  THE  EFFECTS  OF  SELEC- 
TION AND  NUTRITION. 

These  experiments  were  conducted  with  Chrysan- 
themum segetum  (Fig.  118),  Coreopsis  tinctoria  and 
Bideiis  grandiflora  (Fig.  119).  Of  the  former  I  re- 
ceived, in  exchange  from  botanical  gardens,  a  certain 
number  of  packets  of  seeds  from  various  sources.  The 
contents  of  the  various  packets  were  mixed  before  sow- 
ing. This  multiple  origin  showed  itself  clearly  in  the 
number  of  ray-florets;  for  the  curve  expressing  their 
variation  was  not  homogeneous  as  usual  but  had  two 
apices  (Fig.  118  A).  One  peak  was  at  13-14  florets, 
the  other  at  21.  This  must  mean  that  there  were  two 
races  present,  mixed  together.^ 

This  interpretation  was  proved  to  be  correct  in  the 
following  year  (1893)  when,  as  a  result  of  choosing 
seed-parents  from  one  of  the  supposed  races  (the  13- 
rayed  one)  every  trace  of  the  second  peak  disappeared 
(Fig.  118  B).     It  did  not  appear  again  in  1894. 

Two-peaked  curves  occur  also  in  man,  and  here  again 
they  are  regarded  as  the  expression  of  the  incomplete 
fusion  of  types  which  have  interbred  for  many  cen- 
turies.^ Such  curves  have  also  been  observed  by  Bate- 
son^    and    Weldon*    in   their   important    investigations 

*  Eine  sweigipfelige  Variatwnscurve,  Roux'  Archiv  fiir  Ent- 
wickelungsmechanik,  II.  Band,  1895,  P-  52.  See  also  the  second 
volume. 

^Otto  Ammon^  Die  natilrliche  Auslese  beim  Menschen,  1893. 

^Bateson^  Proc.  Zool.  Soc,  London,  1892,  p.  585. 

*Weldon,  loc.  cit. 


Equilibrium  Between  Selection  and  Nutrition.  563 

into  the  variability  of  various  animals  {Forficula,  Car- 
cinus,  Xylotropus,  etc.),  and  repeatedly  by  Ludwig  in 
plants.  Bateson^  in  his  work  on  discontinuous  varia- 
tion, has  emphasized  the  great  importance  of  such  cases 
to  the  student  of  variability,  and  given  examples  of 
them.^  Tbe  two-peaked  curves  are  separated  by  him 
as  cases  of  dimorphism  from  the  ordinary  or  mono- 
morphic  curves. 

The  duplicate  character  of  curves  can  be  brought 
about  by  the  most  various  causes.  Giard,  for  example, 
has  made  the  remarkable  discovery  that  a  dimorphism 
of  this  kind  may  be  brought  about  when  some  of  the 
individuals  in  a  locality  are  infested  by  a  parasite.  Thus 
Carcinus  mocnas  which  were  infected  by  Sacciilina  car- 
cini  or  Portunion  moenadis  differed  widely  from  the 
normal  ones.^ 

But  the  double  curves  in  plants  can  be  dealt  with  ex- 
perimentally much  better  than  those  in  animals  or  men. 

Let  us  now  proceed  to  the  description  of  the  experi- 
ment with  Chrysanthemum  segetum.  In  1892  this  ex- 
tended over  an  area  of  2  square  meters.  The  number 
of  individuals,  when  I  came  to  select  them  was  97.  For 
making  the  curve  only  one  head  was  taken  from  each 
individual,  the  so-called  primary  one  at  the  top  of  the 
main  stem.  All  plants  whose  terminal  inflorescence  had 
14  or  more  ray  florets  were  pulled  up  immediately; 
fourteen  plants  with  13  such  florets  and  one  with  12  were 
saved. 


^W.   Bateson,  Materials  for  the  Study  of  J^an'ation,  London, 
1894,  PP-  39-41- 

Comptes  rendus,  T.  CXVITT,  1894,  No.  16  (April  16).  p.  870. 
This  case  has  now  been  thoroughly  investigated  by  Geoffrey  Smith, 
Fauna  and  Flora  of  the  Gulf  of  Naples.  Volume  on  Rhizocephala 
(Note  of  1908). 


564        Curves  of  Coinpositae  and  Umbelliferae. 


In  1893  the  seeds  of  these  15  plants  were  sown  on 
8  square  meters  of  ground;  162  plants  were  raised.  All 
of  these  were  weeded  out,  with  the  exception  of  12 
plants  whose  terminal  heads  had  11-12  ray  florets.  That 
is  to  say,  the  seed-parents  exhibited  an  advance  in  the 
negative  direction  as  compared  with  the  previous  year. 

CHRYSANTHEMUM  SEGETUM. 


NUMBER  OF  RAY- 

NUMBER  OF  PLANTS 

FLORETS 

1892 

1893 

1894 

8 

0 

2 

0 

9 

0 

1 

1 

10 

0 

0 

3 

11 

0 

7 

8 

12 

1 

13 

31 

13 

14 

94 

221 

14 

13 

25 

50 

15 

4 

7 

8 

16 

6 

7 

5 

17 

9 

1 

4 

18 

7 

2 

3 

19 

10 

0 

1 

20 

12 

3 

2 

21 

20 

0 

1 

22 

1 

0 

0 

The  curve  of  1892  was  therefore  dimorphic ;  those  of  1893  and 
1894  monomorphic.  From  the  two  latter  the  following  data  have 
been  calculated. 


^ears     Seed  parents 

Qi    ' 

M 

Qz 

Q 
M 

1893            12—13 

0.4 

13.1 

0.6 

0.04 

1894                12 

0.4 

13.1 

0.4 

0.03 

Increase 

0.0 

0.0 

—0.2 

In  the  third  year,  1894,  the  culture  occupied  6  square 
meters :  it  was  raised  from  the  seed  of  three  plants  of 
1893,  each  of  which  had  12  rays  in  the  terminal  head, 
and  only  13  in  the  later  ones.  The  number  of  plants  at 
the  time  of  selection  was  338. 


Equilibrium  Between  Selection  and  Nutrition.  565 


1 

B 

J8 

93 

1     ,' 

\ 

1    / 
1    / 

\ 

18 

/ 
/ 

92_ 

'   / 

1 

A 

/ 

/ 

/ 

/ 

i 

\ 

/ 

/ 

/ 

1 

1 

/ 

\ 

/ 

/ 

\ 

8    10    n    u    16    18    no 


Fig.  Ii8.  Chrysanthemum 
segetum.  Curves  of  the  ray- 
florets  of  the  terminal  in- 
florescences. Under  the  ab- 
scissa are  the  numbers  of 
these  florets.  The  number 
of  ordinates  is  reduced  to 
the  half;  8  therefore  means 
7-8  ray  florets  etc.  (height : 
I  mm=i%). 

A  (97  plants)  Dimorphic 
curve  from  a  mixed  sowing 
1892. 

B  (i62plants)  Bythe selec- 
tion of  plants  belonging  to 
the  group  with  13-14  florets 
as  seed-parents  the  curve 
has  become  monomorphic 
in  the  next  generation,  1893. 
— The  curve  for  1894  was 
almost  exactly  the  same  as 
that  for  1893. 


10    11    12 


Fig.  119.  A,  Coriandrum  sativum 
(334  plants).  Curve  of  1894.  The 
numbers  under  the  abscissa  refer  to 
the  number  of  rays  of  the  primary 
umbel.  Height  of  the  ordinates :  I 
mm=i%   of  the  individuals. 

B,  Bidens  grandiiiora  (152  plants). 
Curve  of  1894.  The  numbers  under 
the  abscissa  signify,  in  curves  B  and 
C,  the  numbers  of  ray-florets  in  the 
primary  inflorescences.  Height  as 
in  A. 

C,  Coreopsis  tinctoria  (495  plants). 
Curve  of  1893. 


566        Curves  of  C o in po sitae  and  Unihelli ferae. 

During  these  three  years  the  germinating  power  of 
the  seeds,  and  the  individual  strength  of  the  whole  cul- 
ture increased  considerably.  In  the  first  year  I  only 
got  the  proper  number  of  plants  per  square  meter  by 
sowing  a  large  quantity  of  seed;  in  the  following  year 
less  seed  was  sown  and  the  crop  was  correspondingly 
scanty:  in  1894  more  seed  again  was  sown  and  many 
seedlings  had  to  be  weeded  out. 

The  result  of  these  observations  is  summarized  in 
the  table  on  page  564.     (See  also  Fig.  118.) 

Selection,  we  see,  in  this  case  has  been  unable  to 
effect  any  further  alteration  in  the  mean  or  in  the  am- 
plitude of  variation.  It  has  simply  maintained  the  mean 
at  the  same  point. 

We  come  now  to  Coreopsis  tinctoria  (Fig.  119  C). 
The  inflorescences  of  this  beautiful  composite  have,  as 
a  rule,  8  ray-florets.  Yet  this  number  varies  on  the  same 
individual  as  well  as  from  plant  to  plant.  I  obtained  my 
seeds  in  the  winter  of  1891/92  from  MM.  Vilmorin- 
Andrieux  &  CiE.  of  Paris,  and  tried  simultaneously 
to  increase  the  mean  number  of  ray-florets  by  manuring, 
and  to  diminish  it  by  selection. 

The  result  was  that  the  mean  number  maintained  it- 
self almost  unaltered  at  8,  that  is  to  say  that  the  effects 
of  the  two  opposing  factors  neutralized  one  another. 

My  cultures  in  the  years  1892,  1893,  1894  extended 
over  1,  8  and  6  square  meters  respectively.  I  determined 
no  curve  for  the  first  year;  the  vast  majority  of  the 
plants  had  8  rays;  occasional  ones  9  and  10;  and  fewer 
still  11,  12  or  13.  These  were  all  pulled  up:  I  only 
saved  a  few,  most  of  which  had  7  ray-florets. 

In  1893  I  had  495  plants;  all  those  which  had  8  or 
more  ray  florets  were  pulled  up  as  soon  as  the  rays  could 


Equilibriuni  Between  Selection  and  Nutrition.  567 

be  counted,  and  recorded.  About  60  plants  with  5,  6 
and  7  florets  were  left  over.  Amongst  these  a  further 
selection  was  made  of  those  whose  branches  were  richest 
in  5-7  rayed  inflorescences.  Immediately  after  the  weed- 
ing out  had  taken  place  these  plants  were  deprived  of  all 
inflorescences  which  were  either  in  flower  or  over,  in 
order  that  all  their  seed  might  result  from  pure  fertili- 
zation. Of  the  twelve  plants  thus  treated  I  chose  the 
four  strongest  and  most  fertile  as  seed-parents  for  next 
year's  crop:  their  terminal  inflorescences  had  5,  5,  6  and 
7  ray-florets  respectively,  and  their  lateral  branches  bore 
heads  with  few  rays.  In  1894  I  obtained  from  their 
seeds  256  flowering  plants  and  determined  the  curve  from 
them  in  the  usual  way. 

The  figures  I  obtained  are  summarized  in  the  table 
on  page  568.     (See  also  Fig.  119  C.) 

The  third  experiment  was  carried  out  with  Bidcns 
grandi flora  (Fig.  119  B).  In  this  species  the  inflor- 
escences are  usually  five-rayed,  but  the  number,  here 
also,  is  subject  to  variation  and  wuthin  limits  similar  to 
those  in  Coreopsis. 

In  the  flowers  of  Dicotyledons  the  number  5  is  as  a 
general  rule  remarkably  constant,  and  probably  in  a 
great  many  cases  hardly  subject  to  any  fluctuations.  The 
question  naturally  presents  itself :  why  is  this  number 
inconstant  in  this  case?  This  problem  has  however  not 
yet  been  investigated;  a  solution  of  it  would  of  course 
be  of  fundamental  importance  to  the  student  of  varia- 
bility. ^ 

I  obtained  my  seeds  in  the  winter  of  1891/92  from 
Messrs.  Haage  &  Schmidt  in  Erfurt,  sowed  a  square 

^The  question  Is  whether  a  cyclic  arrangement  diminishes  the 
variability  of  the  number  of  the  parts  involved  and  if  so:  why? 


568        Curves  of  Compositae  and  Umbelliferae* 


COREOPSIS  TINCTORIA. 


NUMBER  OF  FLORETS 

NUMBER  OF  PLANTS 

1893 

1894 

1 

2 
3 

4 

5 

6 

7 

8 

9 

10 

11 

12 

13 

0 
0 

1 

0 

2 

13 

49 

311 

76 

28 

12 

3 

0 

2 

0 

1 

3 

5 

10 

53 

191 

14 

5 

2 

0 

0 

From  which  I  have  calculated  the  following  values 


Year       Seed  parents 

Qi 

M 

Q2 

Q 

M 

1893                  7 

0.4 

8.1 

0.3 

0.04 

1894        5,  5,  6  and  7 

0.5 

7.9 

0.3 

0.05 

Increase 

0.1 

-0.2 

0.0 

meter  with  them  in  1892  and  chose  as  seed-parents  a 
few  examples  on  which  I  had  seen  3  and  4  rayed  in- 
florescences. 

In  1893  I  sowed  8  square  meters  with  their  seeds  and 
got  557  flowering  plants;  and  made  a  curve  of  the  num- 
bers of  rays  of  their  primary  heads.  I  chose  a  series 
of  plants  with  four-rayed  inflorescences  and  when  their 
seeds  were  ripe  made  a  further  selection  of  three  of  them 
which  had  exhibited  the  lowest  numbers  of  rays  in  their 
other  inflorescences. 

From  their  seeds  I  raised,  on  6  square  meters,  152 
flowering  individuals.     I  again  made  a  curve  from  their 


Obliteration  of  Effect  of  Nutrition  by  Selection.  569 

terminal  heads;  and  found  the  figures  given  in  the  table 
on  this  page. 

Here  again  as  in  Chrysanthemum  and  Coreopsis  there 
was  no  marked  effect  on  the  curve  while  nutrition  and 
selection  were  operating  in  opposite  directions. 

BIDENS   GRANDIFLORA. 


DUMBER  OF  RAYS 

NUMBER  OF  PLANTS 

1893 

1894 

2 

3 
4 
5 
6 
7 
8 
9 
10 

1 

10 

31 

355 

113 

40 

6 

1 

0 

2 
8 
16 
117 
6 
2 
1 
0 
0 

Totals 

557 

152 

From  which  I  have  calculated  the  following  values 


^ear     Seed  parent     Q^ 

M 

Qz 

Q 

M 

1893               4              0.4 

5.2 

0.5 

0.09 

1894               4              0.3 

4.9 

0.4 

0.07 

Increase                   —0.1 

-0.3 

-0.1 

§   8.    OBLITERATION   OF   THE   EFFECT   OF   NUTRITION 

BY  SELECTION. 

The  experiment  was  carried  out  partly  with  Corxan- 
drum  sativum,  the  common  Coriander,  and  partly  with 
Madia  elegans,  as  species  related  to  the  oil  Madia  (Madia 
sativa). 

The  seeds  of  the  former  were  obtained  from  MM. 


570        Curves  of  Compositae  and  Umhelliferae, 

Vilmorin-Andrieux  &  CiE.  in  Paris  and  sown  on  a  bed 
of  one  square  meter.  When  I  came  to  select  them  the 
number  of  plants  was  45;  the  vast  majority  had  five 
rays  in  the  primary  umbel,  some  6,  very  few  7  and  8, 
and  none  any  more.  Two  plants  had  four-rayed  ter- 
minal umbels,  and  on  one  of  them  most  of  the  secondary 
umbels  were  also  four-rayed.  I  only  harvested  seed 
from  the  two  latter  plants.    A  curve  was  not  determined. 

Next  year  the  culture  extended  over  two  square 
meters,  and  the  number  of  adult  plants  was  52.  Of 
these  the  great  majority  had  5-rayed  terminal  umbels. 
Of  the  three  plants  which  were  chosen  as  seed-parents 
one  had  a  3-rayed  terminal  umbel,  the  two  others  4-rayed 
ones. 

The  seed  of  these  three  plants  was  sown  separately 
in  1894;  each  lot  on  two  square  meters.  The  number 
of  individuals  at  the  time  of  selection  was  334,  amongst 
which  there  occurred  two  with  a  two-rayed  terminal 
umbel,  a  result  which  means  an  advance  in  a  negative 
direction  on  the  stage  attained  in  the  previous  year;  but 
may,  perhaps,  be  partly  attributed  to  the  larger  number 
of  individuals  in  the  culture.  The  plants  were  harvested 
separately  on  the  three  beds,  but  the  results  are  all  given 
together  in  the  table  on  page  571.  It  is  very  curious 
that  the  offspring  of  the  three-rayed  parent  exhibited 
on  the  average  a  greater  number  of  rays  than  those 
of  one  of  the  two  four-rayed  parents.  The  character 
of  the  parent  is  therefore  only  an  imperfect  guide  of 
the  average  character  of  its  progeny. 

As  shown  in  the  following  table,  selection  has  suc- 
ceeded, in  spite  of  the  heavy  manuring,  in  reducing  the 
number  of  rays  in  the  umbel  by  almost  a  whole  unit. 


Obliteration  of  Effect  of  Nutrition  by  Selection.  571 


CORIANDRUM    SATIVUM     (Fig.    119  A). 

RAYS  IN  TERMINAL  UMBEL 

NUMBER  OF  INDIVIDUALS 

1893 

1894 

2 

0 

2 

3 

1 

43 

4 

8 

146 

5 

30 

133 

6 

12 

10 

7 

1 

0 

From  which 

I  have  calculated 

Year 

Seed  parent 

Qi 

M 

Qz 

Q 

M 

1883 

4 

0.5 

5.1 

0.4 

0.09 

1894 

3,  4  and  4 

0.5 

4.3 

0.6 

0.13 

Increase 

0.0 

-0.8 

-f-0.2 

The  amplitude  of  variation  Q/M  is  intermediate  be- 
tween those  of  Oenothera  (0.08)  and  Anethnm   (0.16). 

We  come  now  to  the  second  series  of  experiments, 
carried  out  with  Madia  elegans. 

This  species  is  more  suitable  for  experiments  with 
selection  than  either  Bidcns  or  Coreopsis.  In  the  first 
place  the  growth  is  much  more  uniform  especially  in 
youth ;  in  the  second,  the  number  of  ray-florets  is  consid- 
erably larger ;  and — last  and  most  important  point  of  all — 
there  is  m^uch  less  partial  variability  in  this  case.  This 
means  that  the  various  inflorescences  on  the  same  ])Iant 
differ  from  one  another  only  slightly  in  the  number  of 
their  rays  (at  least  in  my  race)  so  that  the  numl)cr  on 
the  terminal  inflorescence  can  be  more  justly  regarded 
as  characteristic  of  the  whole  plant. 

I  obtained  the  seeds  from  Messrs.  Ha  age  &  Schmidt 
in  Erfurt.  I  sowed  them  in  1892  over  a  square  meter  of 
soil.      Most  of  the  individuals   had  21    ligulate   florets, 


572        Curves  of  Compositae  and  Umhelliferae. 

many  had  20  or  22,  a  few  had  23  or  25.  These  were 
all  pulled  up.  There  remained  6  plants  with  16-19  rays; 
their  seed  was  harvested  in  autumn. 

In  1893  this  experiment  occupied  8  square  meters. 
I  made  a  curve  of  the  ray  florets  of  411  plants  that  were 
raised  on  it.  Eight  plants  with  13-15  florets  were  chosen 
as  seed-parents. 

Of  these  I  chose  the  best  three  with  13-rayed  terminal 
inflorescences,  sowed  their  seeds  on  6  square  meters  and 
obtained  no  more  than  213  adult  plants  as  a  result  of  an 
accident  by  which  a  number  were  lost.  The  variability 
in  the  number  of  ray-florets  of  these  plants  is  given  in 
the  following  table,  together  with  those  of  the  1893  crop. 

MADIA    ELEGANS. 


NUMBER  OF  RAY -FLORETS 

NUMBER  OF  PLANTS 

1893 

1894 

12 
13 
14 
15 
16 
17 
18 
19 
20 
21 
22 

1 

IS 
11 
18 
18 

43 
63 
101 
82 
54 
5 

0 
12 
16 
18 
20 
29 
32 
50 
23 
12 

1 

Totals 

411 

213 

From  which  I  have  calculated  the  following  values 


Year      Seed  parent 

Q. 

M 

Q^ 

Q 

M 

1893            16—19 

1.5 

18.9 

1.1 

0.07 

1894                13 

2.1 

17.9 

1.3 

0.09 

Increase 

0.6 

—1.0 

0.2 

Summary.  573 

That  is  to  say  a  definite  though  shght  decrease  in  the 
mean  number  as  the  resuh  of  fairly  rigid  selection. 


§  9.   SUMMARY. 

In  conclusion,  I  will  give  the  results  described  in  the 
last  three  sections  in  a  short  summary. 

The  general  result  is  that  they  are  in  complete  har- 
mony with  those  obtained  with  Oenothera  Lamarckiana 
and  O.  rubrinervis  (§§  4-5)  and  can  therefore  be  re- 
garded as  a  confirmation  of  these. 

They  show  that  when  nutrition  and  selection  are 
brought  into  conflict,  in  some  cases  one  of  them  triumphs, 
and  in  others  the  other.  In  Anethum  it  was  nutrition,  in 
Coriandrum  and  Madia  selection,  in  Chrysantheumm, 
Coreopsis  and  Bidens  it  was  a  drawn  battle.  The  differ- 
ences between  the  results  of  the  individual  experiments 
has  evidently  more  to  do  with  the  relative  power  of  these 
two  factors  than  with  any  putative  differences  between 
the  species  investigated.  For  obviously  the  same  amount 
of  manure  per  square  meter  means  a  very  different 
amoujit  of  nutriment  for  different  plants;  and,  on  the 
contrary,  selection,  however  stringent  it  may  be,  is  effec- 
tive in  analogously  different  degrees. 

We  conclude,  therefore,  that  selection  and  nutrition 
influence  the  plant  in  the  same  direction  and  that  it  de- 
pends on  circumstances  whether  the  one  or  the  other  of 
the  two  preponderates. 

Perhaps  the  simplest  and  clearest  way  of  proving 
this  generalization  is  to  exhibit  the  means  of  the  num- 
bers of  rays  and  ray-florets  of  the  primary  inflorescences 
of  all  the  species  investigated. 


574        Curves  of  Coinpositae  and  UmhclUfcrae. 

Increase 
1892  1893  1894        1893—1894 

Aiiethum  graveolens  18.3  21.2  25.2  +4.0 

Chrysanthemum  segetum  13 — 14  13.1  13.1  0.0 

Coreopsis  tincioria  d=8  8.1  7.9  —0.2 

Bide7is  gi^andiflora  ±  5  5.2  4.9  —0.3 

Coriandrum  sativum  ±5  5.1  4.3  — 0.8 

Madia  elegants  ±21  18.9  17.9  -1.0 

The  varying  result  of  the  conflict  between  heavy 
manuring  for  three  years  and  the  selection  of  individuals 
with  a  small  number  of  rays  is  shown  by  the  figures  in 
the  last  column. 

I  shall  now  exhibit  the  values  for  Q/M  in  a  single 
table.  Q,  as  we  have  already  said,  may  be  made  inde- 
pendent of  the  nature  of  the  varying  character  by  di- 
viding it  by  M ;  and  in  this  way  the  amplitudes  of  varia- 
tion of  the  different  characters  may  be  compared  with 
one  another.  The  subjoined  values  for  0/M  are  the 
means  calculated  from  two  or  more  generations  in  all 
the  above  cases.  I  have  added  Oenothera  Lamarckiana 
to  the  list. 

M 

Anethwm  graveole^is 0.16 

Coriandrum  sativmn 0.11 

Oenothera  Lamaixkiafia     ....  0.08 

Bidejis  grajidiflora 0.08 

Madia  elegans 0.08 

Coreopsis  tincioria 0.04 

Chrysanthemum  segetum    .     .     .     .  0.03 

The  observed  amplitudes  of  variation,  estimated  by 
this  measure,  differ  considerably  from  one  another.  But 
they  are,  of  course,  also  affected  by  selection  and  nutri- 
tion. 

The  phenomena  of  fluctuating  variability  are,  there- 


Summary.  575 

fore,  caused  by  these  two  factors.  The  amount  of  hte  devi- 
ation of  any  given  character  from  its  mean  is  determined 
partly  by  selection,  i.  e.,  by  the  characters  of  its  parents  and 
grandparents  and  partly  by  nutrition,  i.  e.,  by  the  ojjcration 
of  external  influences  on  the  individual  itself.  But  the 
characters  of  the  ancestors  were  also  determined  by  the 
conditions  of  life;  so  we  arrive  at  the  conclusion  that 
the  phenomena  of  variability  in  the  strict  sense  of  the 
term,  that  is,  the  individual  deviations  from  the  mean 
of  the  species  are  solely  caused  by  external  conditions. 
Only  it  must  be  remembered  that  nutritional  influences 
may  be  cumulative  over  several  generations,  inasmuch 
as  only  the  best  individuals  will  bear  the  best  seed. 

Fluctuating  variability  therefore  falls  within  the 
province  of  the  physiology  of  nutrition.  The  external 
causes  of  mutation  are,  on  the  other  hand,  as  yet  wholly 
unknown. 


INDEX. 


Abanderungsspielraum,  149. 

Acacia,  363. 

Acclimatization,  86,  92. 

Aconitum  Napellus,  59. 

Acquired   characters,  130,  135, 213 

Adaptation,  149. 

Aesculus  Hippocastanum,  62. 

Affoler,  492. 

Ageratum  mexicanum,  194. 

A  gratis  segetum,  320. 

Alnus  laciniata,  193. 

Alpine  plants,  145. 

Ammon,  149,   154. 

Amphisyncotyly,  476. 

Analytical  tables,  448. 

Anethum  graveolens,  559. 

Animal  kingdom,  3. 

Apples,  179. 

Arctic  plants,  145. 

Ascidia,  470. 

Associated   characters,   329,   375. 

Association  of  units,  3. 

Atavism,  20,  136,  196,  364. 

Atavistic  characters,  311,  362. 

Atavists,  79. 

Aulax  Hieracii,  407. 

Auslese,  Natiirliche,  156. 

Avena  fatua,  98. 

Bailey,  181. 
Barley,  brewer's,  116. 
Barley,   Chevalier,   ill. 
Bateson,  6. 


Beans,  47. 

Beans,  Curve  of,  48. 

Beech,  copper,  192. 

Beets,  Sugar,  99;  Sugar  in  40- 

000,  103. 
Beissner,  364. 
BcUcvue  de  Talavera,  178. 
Beseler,  81. 

Betula  alba   laciniata,   193. 
Beyerinck,  406. 
Bidens  grandiiiora,  562,  567. 
Biscutella  laevigata,  62. 
Blankinship,   56. 
Bleu^  Alfred^  47. 
Bonnier,  144. 
Bourgeons  multiples,  487. 
Brassica  oleracca,  192. 
BucKMANN,  90,   124. 
Bud  variations,  53. 
Buds  on  cotyledons,  488. 
BuRBANK,  115. 

BURKILL^    160. 

Cabbage,  Scottish,   124. 
Caladium,  47. 
Calliopsis  tinctoria,  197. 
Carcinus  mocnas,  563. 
Carriere,  90. 
Carrot,  wild,  89. 
Carter  &  Sons,  496. 
Cclosia  cristata,  125. 
Ccntaurca  Cyanus,  134. 
Cereals,  106. 


578 


Index. 


Characters,  innate,  136;  specific, 

186 
Chelidonium   laciniatum,   189. 
Chrysanthemum  indicum,  99;  sc- 

getum,  151,  562,  565. 
Clos,  360. 
Cockscomb,  125. 

CoefBcients  of  mutation,  337,  351. 
Compositae,  556. 
Conditions,  external,  2)7- 
Constancy,  507. 
Convariants,  51. 
Cope,  62,. 

Coreopsis    tinctoria,   566. 
Correlation,    115,    160,  328. 
Coriandrum   sativum,   569,   571. 
Cornflower,  134. 
Corn,  Tarascora,  95. 
CosTANTiN,  28,  86,  99. 
Cotyledons,  split,  488. 
Crab  apple,  120. 
Crosses,  298,  299,  300. 
Crossfertilization,   76. 
Crossing,  free,  78. 
Curves,  transgressive,  56,  358. 
Cuttings,  386. 
Crowding  of  plants,  139. 
Cyclamen  latifolium,  191. 

Dahlia,  double,  185;  striped,  54. 

Daniel,  161. 

Darwin,   153. 

Darwinism,  39. 

Datura  Tatula,  21,  170. 

Daucus  Carota,  89. 

Davenpobt,  56,  430. 

De  Candolle,  Alphonse,  30,  86. 

Delboeuf,  208,  254. 

Delpino,  186,  364. 

Devariants,  51. 

Dollo,  63. 

Donkelaar,  185. 

Drab  a  verna,  22,  494. 


Duncker,  49,  131,  159. 
Duration  of  selection,  85. 

Elements  of  species,  4. 
Elite,  108. 
Ericksson,  175. 
Eucalyptus  Globulus,  364. 
Eupatorium,  407. 

Fagus,  144. 

Fagus  asplenifolia,  193. 

Fan  Type  of  Plotting,  52. 

Fasciation,  476. 

Fertilization,    153, 

Filaments,  fusion  of,  488. 

Flax  seed,  128.  ■ 

Fleeming  Jenkin,  2>7- 

Fleshiness  in  fruits,   120. 

Flowers,  bimerous,  483 ;   trimer- 

ous,  483 ;   with  bracts,  486. 
ForHcula,  563. 
Forms,  intermediate,  504. 
Fragaria  alpina,  32,   192 ;   mono- 

phylla,  193. 
Fruit  trees,  179. 
Fruits,    pentamerous,    483. 
Fruwirth,  yy. 

Galls,  406. 

Galton,  49,  136;  curves,  half,  51 ; 
median,    525 ;    polyhedron,    53. 
Gandoger,  28,  174. 
Gauchery,  360. 
Gemmules,   38. 
Genealogical  tree,  6. 
Generations,    intermediate,    128. 
Germination,  belated,  261. 
Giard,  153.  *% 

Gideon,  181. 
Godron,  24. 

Groups,   nebulous,   495,   511. 
Groups  of  units,  3. 
GuLiCK,  208. 


Index. 


579 


Haacke,  519. 
Habit,  507. 
Hallett,  1 10. 
Haycraft,  158. 
Hedera  Helix  arhorea,  44. 
Heinsius,  151. 
Helianthemiim  vulgare,  146. 
Herbert,  36. 
Hertwig,  O.,  57,  62,  154, 
Heterogenesis,  68, 
Hieracium,  495 ;    umbellatum,4oy. 
Hitchcock,  437. 
Hoek,  431. 
Hoffmann,  z7- 
Homegrowing,   127. 
Hooker,  58. 
Horn  meal,  537. 

Hybridization,  4,  47,  y6,  96;  laws 
of,  301. 

Ilex  Aquifolium,  196. 
Index  Kewensis,  21. 
Inheritance,  latent,  468. 

Jaggi,  192. 

Jagtlust,  266. 

Janet,  211. 

Jencic  on  pollen  of  hybrids,  418. 

Jenkin,  Fleeming,  37. 

johannsen,  520. 

Jordan,  22,  127. 

KiDD,  157. 
Kleebahn,  167. 
Knight,  133. 
KoBUs,  148. 
Kolliker,  68. 
kollmann,  49,  155, 
Korschinsky,  46,  67. 

KUHN  &  Co.,   102 

Lactuca,  144. 
La  Gasca,  177. 
Lamarck,  17. 


Layering,  116. 

Leaves,  concrescence  of,  485  ;  pel- 
tate, 470;  split,  484. 
Le  Couteur,  177. 
Leveille,  437. 
Lignier,  153. 

LiNDLEY,    127. 

Linnaeus,  20. 
Linum  crepitans,  194. 
Lomaria  proccra,  59. 
LuDWiG,  49,  521. 
LuTZ,  Anne  M.,  325. 
Lysimachia  vulgaris,  407. 

Mac  Leod,  134,  516,  518. 

Madia  elegans,  84,  571. 

Maize,  number  of  rows,  125 ;  of 

Baden,  94;  selection  with,  y2>- 
Malthus,  Essay  on  Population, 

34. 

Mansholt,  van,  127. 

Maple,  cutleaved,  185. 

Matricaria  Chamomilla  discoidea 
196. 

Matthiola  incana,  204. 

Median,  Galton's,  525. 

Mercurialis  laciniata,  192. 

Metzger,  93. 

Migration,   206. 

Minus-variations,  51. 

Modifications,  nutritional,  146. 

Monde  ambiant,  63. 

Monocotyledons,    186. 

MoNS,  VAN,  179. 

Monstrosities,  469;  taxinomiqucs 
469. 

Mueller,  on  Maize.  71. 

MuNTiNG,  127.   182. 

Mutability,  indiscriminate.  205. 
419;  periodic,  205. 

Mutants  arising  from  new  spe- 
cies, 297;  percentage  of  40 ^c . 
264. 


580 


Index. 


Mutation,  24;  coefficients,  415, 
504;  in  nature,  300;  in  pre- 
Darwinian  days,  1 1 ;  laws  of, 
247;  progressive,  6,  68;  retro- 
gressive, 6,  68;  smaller  than 
variations,  55 ;  theory,  3. 

Nanisme,   360. 

Nature    abhors    perpetual     self- 
fertilization,  153. 
Naudin,  36,  169 

NlLSSON^   114. 

Nomen  specificum,  19. 

Nomenclature,  172. 

Nutrition,  and   selection,  515,  536 ; 

and  variability,  516;  Effects  of, 

131;  high,  551. 
Nutritional   modifications,    132, 

Oats,  Anderbecker,  81. 

Oenothera  alhida,  229,  349;  bi- 
ennis, mutation  period,  440, 
495;  biennis,  type,  431;  brevi- 
stylis,  315;  cruciata,  455;  ellip- 
tica,2,92>',  fatua, 419;  gigas,226, 
318;  gigas,  appearing  thrice, 
327 ;  gigas,  chromosomes,  325  ; 
gigas-nanella,  375 ;  hirsutis- 
sima,  455 ;  laevifolia,  308 ;  lae- 
vifolia,  origin  of,  266;  lepto- 
carpa,  353 ;  Lamarckiancu, 
length  of  fruit,  528;  Lam., 
long-fruited  race,  545 ;  La- 
marckiana  nana,  2)^2 ;  Lam.  X 
O.  biennis,  299;  Lamarckiana 
X  O.  nanella,  298;  Lamarck- 
iana, pitcher,  484;  Lamarck- 
iana, premutational  period,  496 ; 
Lam.,  short-fruited  race,  546; 
lata,  239,  310,  402;  lata  na- 
nella, 239,  304;  lataXO.  bi- 
ennis, 299 ;  lata  X  O.  nanella, 
299;   muricata,  type,  431;   na- 


nella, 235,  360;  nanella  ellip- 
tica,  239 ;  nanella  lata,  374 ;  na- 
nella oblonga,  239,  375 ;  na- 
nella scintillans,  375 ;  oblonga, 
234,  284,  2>2>7;  rubrinervis,  230, 
282,  z^7 ;  scintillans,  243,  yjy ; 
scintillans-nanclla,  375;  semi- 
lata,  358;  spathulata,  419;  sub- 
linearis,  399;  subovata,  419. 

Oenotheras,    Anatomy    of    the 
stem,  335;  seeds  of,  437. 

Ogive,  49. 

Oleaster,  124. 

Olive,  124. 

Othonna  crassifolia,  145. 

Oxalis   corniculata,  58. 

Pangenesis,  38,  39;  Intracellu- 
lare,  57,  61. 

Papaver  bracteatum  monopeta- 
lum,  16;  dubium,  175;  somni- 
feriim  polycephalum,  138. 

Parsnip,  90,  124. 

Partial  fluctuation,  6;  variability, 

143- 
Pastinaca  sativa,  124. 
Pears,  179. 
Pearson^  157. 
Peas,  123. 
Pedigrees,  503. 
Pelargonium  zonale,  195. 
Period,  susceptible,  519. 
Periods,  mutation,  207. 
Periodicity,   Darwin's   belief  in, 

36. 
Petalomany,  195. 
Phaseolus  vulgaris,  47. 
Phyt Optus,  407. 
Pitchers,  61,  470,  485. 
Pliny,  176. 
Ploetz,  50,  131. 
Plusia  gamma,  320. 
Plus-variations,  51. 


Index. 


581 


POHL,    219,    240,    315,    408. 

Polymery,  481. 

Polymorphism,   173;   by  hybridi- 
zation, 46;   systematic,  45. 
Portunion  mocnadis,  563. 
Pofentilla   Tormcntilla,   174. 
Premutation,  490,   510. 
Primula  acaiilis,  20;  veris,  20. 
Probstei,   108. 

Propagation,  vegetative,  82. 
Prophylls,  487. 
Proskowetz,  von,  520. 
Prunus  Lauro-Cerasus,  49. 
Pterophorus,   407. 

Quartile,  526. 
Quetelet's  law,  47. 

Races,  Instability  of,  120. 

Radish,  wild,  90. 

Ramsay,  335. 

Ranunculus   acris   pctalomana, 

194 ;   arvensis  inermis,  196. 
Ray-florets,  556. 
Regression,  ^z,  88,  120. 
Reinke,  364. 
Retrogression,  123. 
Reversion  to  mediocrity,  95. 
RiMPAU,  96. 
RiSLER,  96. 

Rivett's  bearded  wheat,  98. 
Rogues,  78. 
Rosa,  495. 
RozE,  E.,  321. 
Rub  us,  495. 

RiJMKER,  Kurt  von,  91. 
Running  out,  96. 
Russell,  487. 
Rye,    Schlanstedt,    113. 

Sacciilina  carcini,  563. 
Saint-Hilaire,  17. 
Salter,  147. 


Saplings,  493. 

Saxifraga   crassifolia,  61. 

Scahiosa  atrupiirpurca,   197. 

Schaafhausen,  36. 

Schindler,  520. 

Schubeler,  98. 

Scott,  W.  B.,  66,  201, 

Sedum  crispum,  182. 

Seeds,  153;  Change  of,  126;  orig- 
inal, 126. 

Seelhorst,  vox,  519. 

Selection,  agricultural  and  horti- 
cultural, 77;  and  nutrition,  562; 
cessation  of,  122;  empirical, 
107;  in  a  minus  direction,  140; 
in  agriculture,  79;  in  the  field, 
122;  limits  of,  119;  method  of, 
121;  methodical,  108;  theory, 
28. 

Semper,  63.  , 

Scnccio  Jacohaca,  172. 

Sensitive  period,  161. 

Serres,  Olivier  de,  176, 

Shirreff,  178. 

Slum  latifolium,  364. 

Six,  266. 

Social  questions,   154. 

Spach,  437. 

Species,  elementary,  57,  167,  171; 
incipient,  416;  inconstant,  zyj; 
Linnean,  20;   sterile,  402. 

Specific  characters,  186. 

Spencer,  59,  i35»  I54.  212. 

Spinacia,  204. 

Spontaneous  changes,  53. 

Sports,  5. 

Stahl,  144. 

Sterility,   417. 

Strawberries,    Gaillox,   32.    192. 

Struggle  for  existence,  212. 

Subspecies,  45,   165,   171. 

Substitution.  4. 
I    Subvariations.  Delpixo.  312. 


582 


Index. 


Sugar  beets,  50,  99;  cane,  148. 
Survival  of  the  fittest,  59,  212. 
Svalof,  114. 
Synanthy,  485. 
Syncotyly,  476. 

Syringa    vulgaris    azurea    plena, 
184. 

Tilia  parviHora,  470. 

TOURNEFORT,    1 8. 

Transitions,  504. 

Transmutability,  205. 

Transmutation  theory,   16. 

Treub^  407. 

Tricotyly,  474. 

Triticum   turgidum   compositum, 

125- 
Typha  latifolia,  56. 

Umhelliferae,  556. 
Units,  3 ;  systematic,  18. 

Van  den  Berg^  184. 
Variability,   43 ;    fluctuating,   49 ; 

individual,   47;     in   man,    154; 

linear,    51;      partial,    49,    143; 

transgressive,  426,   430. 
Variation,  amplitude,  525  ;  chance 

35 ;  continuous,  6 ;  correlative, 

160;    discontinuous,   51;   grad- 


ual, 5;  linear,  118;  meristic, 
51;  single,  53;  slight,  34;  spon- 
taneous,  165. 

Variegation   of  leaves,  408,  480. 

Variegated  plants,    147. 

Varietates  minores,  21. 

Varieties,  169,  360,  506;  are  only 
small  species,  171 ;  character- 
istics of,  252;  sterile,  195. 

Verschaffelt,  242,  527. 

ViLMORIN,    83,    89,     100,    492. 

Viola  arvensis,  24;    tricolor,  23. 
Virescence,  407,  423,  472. 

Waagen^  50,  66. 

Wagner,  206. 

Wallace,  12,  39. 

Watson,  124,  437. 

Weisse,  518. 

Wettstein,  R.   von,  91. 

Wheat,  177;  Galland,  96;  Pedi- 
gree, III;  Rivett's  bearded, 
89 ;  Smyrna,  125  ;  talavera,  109 ; 
Zeeland,    128. 

WiER,  185. 

Yellow  seedlings,  481. 

Zca  Mays,  72 ;  sterilis,  195 ;  tuni- 
cat  a,  60. 


Second  Edition,  thoroughly  Corrected 
and  Revised,  with  Portrait. 

SPECIES  AND  VARIETIES 

Their  Origin  by  Mutation 

By  Hugo  de  Vries. 
Professor  of  Botany  in  the  University  of  Amsterdam. 

Price,  postpaid  $5.00   (21s.)   net.     xxiii+830  pages,  8vo., 

cloth,  gilt  top. 

The  belief  has  prevailed  for  more  than  half  a  century 
that  species  are  changed  into  new  types  very  slowly  and 
that  thousands  of  years  are  necessary  for  the  development 
of  a  new  type  of  animal  or  plant.  After  twenty  years  of 
arduous  investigation  Professor  de  Vries  has  announced 
that  he  has  found  that  new  species  originated  suddenly  by 
jumps,  or  by  "mutations,"  and  in  conjunction  with  this  dis- 
covery he  offers  an  explanation  of  the  qualities  of  living 
organisms  on  the  basis  of  the  conception  of  unit-characters. 
Important  modifications  are  also  proposed  as  to  the  con- 
ceptions of  species  and  varieties  as  well  as  of  variability, 
inheritance,  atavism,  selection  and  descent  in  general. 

The  announcement  of  the  results  in  question  has  excited 
more  interest  among  naturalists  than  any  publication  since 
the  appearance  of  Darwin's  Origin  of  Species,  and  marks 
the  beginning  of  a  new  epoch  in  the  history  of  evolution. 
Professor  de  Vries  was  invited  to  deliver  a  series  of  lectures 
upon  the  subject  at  the  University  of  California  during  the 
summer  of  1904,  and  these  lectures  are  offered  to  a  public 
now  thoroughly  interested  in  modern  ideas  of  evolution. 

The  contents  of  the  book  include  a  readable  and  orderly 
recital  of  the  facts  and  details  which  furnish  the  basis  for 
the  mutation-theory  of  the  origin  of  species.  All  of  the 
more  important  phases  of  heredity  and  descent  come  in  for 
a  clarifying  treatment  that  renders  the  volume  extremely 
readable  to  the  amateur  as  well  as  to  the  trained  biologist. 
The  more  reliable  historical  data  are  cited  and  the  results 
obtained  by  Professor  de  Vries  in  the  Botaniwil  Garden  at 
Amsterdam  during  twenty  years  of  observation  are  de- 
scribed. 

Not  the  least  important  service  rendered  by  Professor 
de  Vries  in  the  preparation  of  these  lectures  consists  in  the 


indication  of  definite  specific  problems  that  need  investiga- 
tion, many  of  which  may  be  profitably  taken  up  by  anyone 
in  a  small  garden.  He  has  rescued  the  subject  of  evolution 
from  the  thrall  of  polemics  and  brought  it  once  more  within 
reach  of  the  great  mass  of  naturalists,  any  one  of  whom 
may  reasonably  hope  to  contribute  something  to  its  advance- 
ment by  orderly  observations. 

The  text  of  the  lectures  has  been  revised  and  rendered 
into  a  form  suitable  for  permanent  record  by  Dr.  D.  T.  Mac- 
Dougal  who  has  been  engaged  in  researches  upon  the  sub- 
ject for  several  years,  and  who"  has  furnished  substantial 
proof  of  the  mutation  theory  of  the  origin  of  species  by  his 
experimental  investigations  carried  on  in  the  New  York 
Botanical  Gardens. 


A  New  Book  by  Prof.  De  Vries 

PLANT   BREEDING 

Comments  on  the  Experiments  of 
NILSSON  AND  BURBANK 

By 

Hugo  De  Vries,  Professor  of  Botany  in  the  University  of 

Amsterdam. 

A  scientific  book  in  simple  language.  Intensely  interest- 
ing as  well  as  instructive.  Of  special  value  to  every  botanist, 
horticulturist  and  farmer. 

Pp.  XV+360.  Illustrated  with  114  beautiful  half-tone 
plates  from  nature.  Printed  on  fine  paper,  in  large  type. 
Cloth,  gilt  top.    Price,  $1.50  net.    Mailed,  $1.70. 

MAN  A  CREATOR. 

If  man  can  truly  be  said  to  have  been  created  in  the 
image  of  God,  he  ought  to  evince  his  divinity  by  imitating 
the  creator  in  deeds  of  creation,  and  this,  indeed,  has  long 
been  recognized  as  the  worthiest  occupation  of  man.  The 
poet,  the  artist,  the  inventor,  in  fact  all  original  thinkers 
and  leaders,  produce  new  forms,  new  devices  and  contri- 
vances, new  thoughts  and  higher  ideals.     Indeed  it  seems 


as  if  the  world  were  the  mere  raw  material  purposely  left 
unfinished  so  as  to  enable  man  to  exercise  the  divinest  of 
his  qualities,  his  creativeness.  The  imperfections  of  nature 
appear  from  this  point  of  view  as  if  made  on  purpose  so  as 
to  offer  man  the  opportunity  of  accomplishing  this  ambitious 
task  and  building  up  a  human  world  above  the  natural.  A 
late  Latin  proverb  characterizes  the  pride  of  the  inhabitants 
of  the  Netherlands  in  this  line: 

Deus  creavit  mare  sed  Batavus  litora  fecit. 

"God  created  the  ocean,  but  the  shores  have  been  made  by 

Batavians." 

The  creativeness  of  man  appears  to  acquire  a  special  re- 
semblance of  God's  own  work,  when  it  extends  to  the  pro- 
creation of  new  species,  and  this  has  actually  been  accom- 
plished of  late  by  Dr.  Nilsson,  the  Director  of  the  Swedish 
Agricultural  Station  at  Svalof,  and  our  reputed  countryman 
Luther  Burbank,  of  Santa  Rosa,  California.  However  meri- 
torious these  undertakings  are,  they  remain  exposed  to  the 
criticism  of  the  narrow-minded,  so  we  need  not  be  sur- 
prised to  find  that  Mr.  Burbank  was  once  called  to  account 
for  arrogance  by  some  ignorant  clergyman  who  for  the  pur- 
pose of  censuring  him  in  the  name  of  God,  invited  him  one 
Sunday  to  his  church,  gave  him  a  prominent  seat  in  a  pew 
exposed  to  the  view  of  the  congregation  and  denounced  the 
supercilious  ways  of  men  who  meddled  with  the  plans  of 
God  by  attempting  to  create  new  species.  The  incident  is 
referred  to  by  Mr.  Harwood  in  his  New  Creations  in  Plant 
Life,  (pp.  20-21)  when  he  speaks  of  the  troubles  which  Mr. 
Burbank  encountered  at  the  start  of  his  career.    He  says : 

"Opposition  now  came  from  many  quarters.  Not  only 
did  his  friends  see  the  fulfillment  of  their  predictions, — 
some  of  them  very  kindly  telling  him  so, — but  people  who 
had  heard  of  some  of  the  strange  things  he  had  done  and 
who  had  not  the  breadth  of  vision  to  see  what  manner  of 
man  this  was,  pronounced  him  a  charlatan. — a  man  who 
was  creating  all  manner  of  unnatural  forms  of  life,  mon- 
strosities, indeed  a  distinct  foe  to  the  race.  A  minister  in- 
vited Mr.  Burbank  to  listen  to  a  sermon  on  his  work,  and 
when  the  guest  was  in  the  pew  denounced  him  in  bitter 
fashion  as  a  man  who  was  working  in  direct  opposition  to 
the  will  of  God,  in  thus  creating  new  forms  of  life  which 
never  should  have  been  created,  or  if  created,  only  by  God 
himself." 


The  incident  is  comical  enough,  but  it  was  not  so  humor- 
ous to  Mr.  Burbank  at  the  time  when  his  only  consolation 
was  the  hope  of  proving  to  the  world  that  his  hopes  were 
not  the  useless  dreams  of  a  visionary,  but  definite  ideals 
the  realization  of  which  would  raise  mankind  a  step  higher 
in  civilization  and  actualize  its  divinity  in  a  more  complete 
sense. 

Burbank's  work  stands  now  before  the  world  and  needs 
no  further  recommendation.  He  found  out  by  experience, 
that  to  be  a  business  man  is  one  thing  and  to  work  for  an 
ideal  is  another.  He  found  that  the  business  part  had  to  be 
neglected  for  the  sake  of  accomplishing  the  great  task  so 
near  to  his  heart,  and  for  this  purpose  Mr.  Carnegie  has 
come  to  his  assistance  by  keeping  a  scientific  station  in  Santa 
Rosa  and  aiding  his  work  in  general.  Much  has  been  writ- 
ten on  Mr.  Burbank,  but  mostly  in  a  popular  way  by  literary 
authors.  Professor  de  Vries,  however,  has  done  justice 
to  the  significance  of  his  labors  from  the  scientific  stand- 
point in  his  new  book  on  Plant  Breeding.  p.  c. 

THE    OPEN     COURT    PUBLISHING    CO. 
378-388  Wabash  Ave. 
Chicago 

Readers  may  secure  copies  of  this  book  in  Eastern  and 
Southern  states  through  the  Baker  &  Taylor  Co.,  33-37  East 
Seventeenth  Street,   New  York,  or  direct  from  the  publishers. 

ntOPERTY  LIBRART 

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